SEX EDUCATION AND THE EFFECT ON TEEN PREGNANCY
Elizabeth Bessman
B.A., Sonoma State University, 2003
B.S., Sonoma State University, 2003
THESIS
Submitted in partial satisfaction of
the requirements for the degree of
MASTER OF ARTS
in
ECONOMICS
at
CALIFORNIA STATE UNIVERSITY, SACRAMENTO
FALL
2010
SEX EDUCATION AND THE EFFECT ON TEEN PREGNANCY
A Thesis
by
Elizabeth Bessman
Approved by:
__________________________________, Committee Chair
Jonathan Kaplan, Ph.D
__________________________________, Second Reader
Craig A. Gallet, Ph.D
____________________________
Date
ii
Student: Elizabeth Bessman
I certify that this student has met the requirements for format contained in the University format
manual, and that this thesis is suitable for shelving in the Library and credit is to be awarded for
the thesis.
__________________________, Department Chair ___________________
Mark Siegler
Date
Department of Economics
iii
Abstract
of
SEX EDUCATION AND THE EFFECT ON TEEN PREGNANCY
by
Elizabeth Bessman
This study uses the National Educational Longitudinal Study from 1988 to assess
whether the probability a teen girl becomes pregnant is related to sex education taught in
school. It is an important question. Teen pregnancy costs the United States at least $7
billion a year. Some people speculate we should educate our children about sex to reduce
the rate of teen pregnancy. Others argue sex education may cause an increase in teen
pregnancies.
This study consists of two parts. First, this study tests to determine if sex
education is endogenous, that is whether a high rate of teen pregnancies in a community
leads to policies promoting sex education programs. A two-stage least squares model is
used to address the endogeniety concern. The Hausman test for endogeniety fails to
reject exogeniety.
iv
The analysis proceeds by conducting panel data analysis involving grade fixed
effects. By using fixed effects, the analysis can control for differences over each grade
that affects all students similarly. The results from this latter analysis fail to show a causal
link between sex education and teen pregnancy.
_______________________, Committee Chair
Jonathan Kaplan, Ph.D
_______________________
Date
v
ACKNOWLEDGMENTS
It is a pleasure to thank the many people who made this thesis possible.
First and foremost, it is difficult to express all my appreciation to Dr. Jonathan Kaplan
and Dr. Craig Gallet. Without their support and great efforts, I would have not finished
this thesis. Both believed in me and for that I will always be grateful.
I thank Michael Alexander; you are the definition of a true friend.
I thank my entire family for providing a loving and supportive environment for me.
I thank my best friend and my love, Roland Coronado.
Lastly, and most importantly, I thank my Pop. To you I dedicate this thesis.
vi
TABLE OF CONTENTS
Page
Acknowledgments.................................................................................................................... vi
List of Tables ........................................................................................................................ viii
Chapter
1. INTRODUCTION …...………..………………………………………………………… 1
2. LITERATURE REVIEW ................................................................................................... 4
3. EMPIRICAL MODEL AND DATA ................................................................................ 18
4. EMPIRICAL ANALYSIS ................................................................................................ 32
5. CONCLUSION ................................................................................................................. 49
References ............................................................................................................................... 51
vii
LIST OF TABLES
Page
1.
Table 3.1 Instrument Variables…………………...…………………………….. 25
2.
Table 3.2 Sex Education by Grade…………….……………………………...... 26
3.
Table 3.3 Individual Characteristics ………...………….……………….…….. 26
4.
Table 3.4a Family Characteristics- Income….……………………...………….. 28
5.
Table 3.4b Family Characteristics- Sister Has a Child..……………….…..….... 28
6.
Table 3.4c Family Characteristics- Parents’ Education……………………....….29
7.
Table 3.4d Family Characteristics- Ethnicity ………...…..…………..……….. 29
8.
Table 3.4e Family Characteristics- Religion….…………………...………..….. 29
9.
Table 3.5 Outside Influences...…………………...………………………..….... 30
10.
Table 4.1a Baseline Probit Results- Individual Characteristics ……..……...….. 35
11.
Table 4.1b Baseline Probit Results- Family Characteristics ………...…..…….. 36
12.
Table 4.1c Baseline Probit Results- Outside Influences ………………….…..... 37
13.
Table 4.2a Test for Endogeneity- Individual Characteristics………………....... 39
14.
Table 4.2b Test for Endogeneity- Family Characteristics ………...………..…. 40
15.
Table 4.2c Test for Endogeneity- Outside Influences ……………...………..….41
16.
Table 4.3a Fixed Grade Effects Model Results- Individual Characteristics …….43
17.
Table 4.3b Fixed Grade Effects Model Results- Family Characteristics….…..... 44
18.
Table 4.3c Fixed Grade Effects Model Results- Outside Influences…..…..….…45
viii
1
Chapter 1
INTRODUCTION
Pregnant teenage girls are not a new problem. Sex education is not new either, nor
is the debate over whether sex education should be taught to students in the classroom.
Sex education was first taught in public classrooms in 1930 because of “The Children’s
Charter” part 10 created at the White House November 22, 1930. In 1932 the first article
questioning what should be taught in the classroom about sex education appeared. The
question of whether to offer sex education to teenagers in the classroom continues to this
day.
Teen pregnancy is an important economic, social, and political matter.
Approximately one million US teenage girls become pregnant each year (Planned
Parenthood, 2009), and of those girls, more than half of them are 17 years old or younger.
According to the Alan Guttmacher Institute (2002), the US teenage pregnancy rate is
among the highest of the industrialized nations. The annual social cost for each child born
by a teenage mother averages approximately $4,750 (Planned Parenthood, 2009). This
number is based on estimates of $2.2 billion per year in welfare and food stamps, medical
costs of $1.5 billion, foster care costs of $900 million, and lost tax revenue of $1.3
million because of lost productivity of teenage mothers. This total cost is over $5 billion
per year.
The literature suggests that there are many factors which affect the rate of teen
sexual activity and pregnancy: religion, socio-economic status, peer pressure, and the
media to name a few. All of these should properly be studied if the goal is to decrease the
2
amount of teen pregnancy. It is also important to realize that sex education itself is not a
homogenous commodity. Policies and standards vary between states and even vary
between school districts within the same state. It is worth noting that the teen pregnancy
rates started to decline in 1990, however, in 2006 teen pregnancy rates began increasing
(The Guttmacher Institute, 2006). This study, while controlling for other factors, will
focus primarily on the effect of sex education.
Numerous studies investigate sex education and teen pregnancy, but only a few
papers (Oettinger, 1991; Kirby, 1981) have examined econometrically how sex education
influences teen pregnancy in the US. This leaves room for considerable empirical and
theoretical contribution on the subject. This thesis adds to the literature by evaluating
econometrically how sex education influences teen pregnancy using the 1998 National
Educational Longitudinal Study (NELS-88) data set for the first time. This thesis is also
the first to consider the possibility of endogeneity of sex education.
It is hoped that a better understanding of the value of sex education in preventing
pregnancy will better inform the debate over sexual education. If a relationship between
sex education and teen pregnancies is determined, then policy makers can make decisions
about sex education and other possible options to reduce teen pregnancies.
The analysis in this thesis is based on a two-part test. First, I test for endogeniety.
This is a necessary part of determining causality since it is possible that higher levels of
teen pregnancy could cause policy makers to implement sex education programs, and
thus a higher level of sex education being associated with a high level of teen pregnancy
which might result in a misleading inference that the education caused the pregnancies,
3
rather than the other way around. The thesis then uses panel data methods to control for
grade fixed effects. These effects control for differences over grades that affect all
students the same. The initial hypothesis leading to this thesis was that the more a
teenager has sex education the less likely they were to become pregnant. However, as is
explained later in this paper, the results proved to be inconclusive.
The thesis is organized as follows: Section 2 reviews the literature on sex
education and teen pregnancy to provide a theoretical and methodological basis for this
study. This review also provides insight into specification of the estimation model.
Section 3 presents estimation issues and a summary of data. Section 4 presents the results
of the empirical analysis. Section 5 summarizes the results of the study.
4
Chapter 2
LITERATURE REVIEW
This literature review is divided into four sections to better explain the effect of
prior studies on the direction and variable selection of this thesis. Section 2.1 reviews
published studies that evaluate previous studies and programs. Section 2.2 discusses
studies on what influences a teenager, and specifically, what influences a teenager to
engage in sexual activity. Section 2.3 describes research closely related to this thesis.
Section 2.4 summarizes the major findings of the literature and identifies gaps in the
literature. Most of the literature throughout the review relating to teen behavior comes
from other disciplines such as psychology or health. The analysis in this study
empirically estimates some of the claims made in these other disciples such as the more
television watched, the more likely a teen girl will become or, if an older sister has a
child, is more likely to become pregnant.
2.1. Published Research Evaluating Previous Studies and Programs
Scales and Kirby (1981) review 27 sex education programs throughout the US. The
review includes Planned Parenthood programs, church-sponsored activities, state and
local government courses, and other programs. They categorized programs as follows:
Planned Parenthood Affiliates, National Youth Organizations (non-church affiliated such
as YMCA, Boys Club), Local Youth Agencies (e.g. The Door), Religious Organizations,
Adult Organizations with a Concern for Youth (e.g. The Population Institute), State and
Local Government Departments, Programs for Pregnant Teens/Teen Parents, and
5
Hospital Programs. Information was then gathered on the structure of the programs,
content being taught, and evidence there was success from each of the selected programs.
A major finding from their review is that there is a general lack of communication
and coordination among programs. This lack of cohesion is most often between school
programs and non-school programs. By not coordinating between the school and nonschool programs, conflicting or mixed messages are likely being taught to the teenagers.
Another major finding is the difference in amount of time used to cover sex
education. Schools typically engage via a planned curriculum using scientific and
educational media approved by an education board. Non-school programs use small
groups, counseling, role-playing, and a variety of media materials such as short films and
pamphlets. School programs may vary in length between a one-time session and an entire
semester or specialized class depending on the school; while the non-school programs
range from one-time sessions to meeting several times a month during a school year.
Additionally, Scales and Kirby (1981) found non-school programs have more
flexibility in what they can teach to teenagers, which allows for a much broader range of
topics but are supported by groups, either religious organizations, city programs, or
teachers and parents who share the same values and beliefs in regards to premarital sex
and birth control. They observed that non-school programs usually have less structure
than the school programs and this has been found to maintain teenagers’ attention, which
leads to more effective at reducing the risk of teen pregnancy. While differing greatly in
structure, similarities were discovered: most school and non-school programs do not
discuss abortion, but both do discuss what is behind making the decision to become
6
sexual1y active, feelings, personal beliefs and values, sexually transmitted diseases, birth
control, human reproductive anatomy, teenager romantic relationships, and other
relationships such as with parents and other trusted adults. Though not adding much in
progressing the evaluation of earlier work, these studies have contributed to the variables
chosen for this analysis: personal beliefs and values and the relationship a teenager has
with an adult.
While Scales and Kirby (1981) focus on the evaluation of programs that teach a
variety of sex education, Macdonald (1987) first focuses on where sex education is
failing and then discusses an approach to reduce teen pregnancy. According to
Macdonald (1987), sex education is failing because mixed messages are being sent by
parents, schools, and other public agencies, however, only one message is not likely to
work for all teenagers. Macdonald (1987) argues just because teenagers are given
information, does not mean teenagers will make the best decision, nor does this mean that
teenagers will not give in to peer pressure. Finally, Macdonald suggests that sex
education is failing because the media influences teenagers, and the media should only
show abstinence-on1y programs on television shows.
Macdonald (1987) believes that in order to reduce teen pregnancy parents must get
involved and talk with their children about sex. He goes on to say schools should work
with parents, not substitute for parents, so there is a cohesive message about sex. Further
Macdonald (1987) claims non-school programs should also work together and work with
parents by having health care providers inform parents about sexual activity, including
different forms of birth control, sexually transmitted diseases, and reasons why teenagers
7
engage in sexual activity. Moreover, teachers, clergy, and other community groups
should not give a different message about safe sex, abstinence, and birth control than
what parents are teaching their children. Due to the variety amongst teenagers, one
message alone will not work; rather one that is tailored and targeted, while keeping the
core message intact, is likely to work. Finally, Macdonald (1987) suggests reasonable
influences on a teenager, such television programming, can increase a teenager’s
likelihood of engaging in risky sexual behavior and of teenage girls becoming pregnant.
Macdonald’s findings have contributed to this thesis’ inclusion of influences, particularly
entertainment media, as an explanatory variable. While seeming wholly disparate;
negative influences and pressure from parents, peers, and entertainment can all have the
same effect of increasing a teenagers likelihood of pregnancy.
Christopher and Roosa (1990) question if teaching abstinence only is enough to
reduce teen pregnancy by evaluating the effects of the Success Express program. This
program is a series of six sessions that focus on instilling premarital abstinence-only
views, increasing self-esteem, teaching teenagers how to communicate effectively with
others, providing reproductive knowledge, and building an awareness of pressures to
engage in sex. Of the 321 teenagers that took part in the program, most of the participants
were either in sixth or seventh grade, and are, on average, 13 years old. Additionally,
69% of those who took part in the program were Hispanic, 21 % were black, 8% were
Caucasians, and 2% were Native American. The average median family income of the
eight program sites was $12,688, with a base year of 1986, Christopher and Roosa (1990)
used a quasi-experimental control group design to evaluate self-esteem, family
8
communication, premarital sexual behaviors, and premarital and marital sexual attitudes.
Only data for teenagers who completed both the pre-test and post-test were
included in the analyses. A comparison of the pre-test and post-test scores to the control
groups revealed that teaching only a single approach to sex education may not be
effective. Christopher and Roosa (1990) argue Hispanics and teenagers from low-income
families are more likely to become pregnant that any other ethnicity and any other socioeconomic background because when they post-tested, most of the pregnant teens came
from low-income families and Hispanic families. They also concluded that a greater
emphasis should be placed on teaching more than one approach to sex education in a
sensitive manner and to motivate more teenagers to participate in such programs that
provide sex education. This thesis considers student ethnicity and different socioeconomic levels to see if they are factors in explaining the probability that a teenage girl
becomes pregnant. Following from Christopher and Roosa (1990), this thesis expects
teenagers from low-income families will be more likely to become pregnant than
teenagers from high-income families; and furthermore, Hispanic teenagers and those that
are not Caucasian to be more likely to become pregnant than Caucasian teenagers.
Like Kirby et al. (1981), East (1999a, 1999b) evaluates the correlation between sex
education and teen pregnancy and programs that have verified some level of success with
teenagers engaging in sexual activity and using birth control. Unlike Kirby et al. (1981),
East (1999a, 1999b) also examines the influence an older pregnant sister has on younger
siblings. East (1999a, 1999b) begins by categorizing three different types of families:
families without a pregnant teenage girl, families with a teen girl who is currently
9
pregnant, and families with a teenage girl who had a baby within the past six months.
East (1999a, 1999b ) includes different ethnicities in the analysis. The results of this
study reveal that a teenager who becomes pregnant and gives birth affects not only the
teenage girl, but also indirectly affects the other children.
When a household includes a pregnant teenager and eventually a new baby, East
(1999a, 1999b) asserts that the mother of the pregnant teenager will not have the same
amount of time to supervise or talk with the other younger children as before the
pregnancy. As such these younger children are more likely to follow the same path of
engaging in sexual activity and any younger sisters are more likely to become pregnant.
East (1999a, 1999b) goes on to suggest that these younger siblings are more likely than
other youths at the same age, ethnicity, and socioeconomic status to have other behavior
problems, such as using drugs and drinking alcohol. This leads to an even greater
likelihood of the younger siblings becoming pregnant, becoming an even greater target
for pregnancy prevention (East, 1999a, 1999b). This study dictates the necessity of
considering household income, but more importantly how having an older sister with a
child influences a younger sibling. This thesis challenges the above findings through the
creation of a new influence, the struggling older sister (money to provide for the baby,
day care, and giving up their own personal life) which should reduce the probability a
younger sibling will engage in risky sexual behavior and thus the likelihood of becoming
pregnant.
Kirby (2002a) reviews studies that examine the influence of school involvement,
characteristics, specific programs that do and do not impact sexual activity, and specific
10
programs that address sexual activity. Kirby (2002a) finds that schools with programs
which reduce the high school dropout rate, increase a teenager's desire to attend school,
such as extracurricular sports, a school's performance in sports and academics, and
ambitions of either attending college or obtaining a decent paying job, are likely to either
postpone when teens begin being sexual activity or increase their usage of birth control,
which decreases teen pregnancy. He also found that those schools with sex education and
sexually transmitted disease/human immunodeficiency virus (STD/HIV) education
programs can postpone teenagers from engaging in sexual activity, reduce the frequency
of sexual activity, or increase the use of birth control, which lowers teenagers becoming
pregnant. Kirby (2002a) also discovered that school clinics and school with programs that
distribute condoms do not increase the sexual activity of teenagers. Similar to other
findings, schools that have poorer students have a higher likelihood of teenage girls
becoming pregnant (Kirby, 2002a). This thesis also includes extracurricular activities
and, like Kirby, expects the more active a teenager is in extracurricular activities, the less
likely the teenager will become pregnant.
Kirby (2001) goes on to review 73 studies, which are not associated with a school,
in which he concludes that one message for teenagers is not effective given teenager
engage in sexual activity for various reasons. Any narrowly-focused program then cannot
be effective at reducing teen pregnancy because it cannot address the multitude of causes
for teen pregnancies. This is specifically important to this thesis since this thesis
determine how effective sex education is in the classroom while controlling for other
factors that are likely to influence the likelihood of pregnancy during the 8th through 12th
11
grades of school.
2.2 Influential Factors
While hormones play a large role in teenager behavior, other influences, such as
self-esteem, family dynamics, what is watched on the television, and the relationships
between a teenager and their peers, family members, and other adult figures, may also
play a role. The following sections describe how each these additional factors influence a
teenager.
2.2a. Self Esteem
Hayes (1995) relies on three British publications and personal beliefs to discuss
how self-esteem, while difficult to quantify, is crucial in making decisions about risky
behavior. She points out how young girls require more attention at a younger age with
regards to their bodies and reproductive organs. Without this addition attention, girls are
less likely to fully understand how their body works. She goes on to argue that sex
education should be unbiased, for example, by not telling young girls that people who use
birth control are sinners. Otherwise, young children will invent creative solutions to
unanswered questions that can lead to misunderstandings and fright about sex. While
Hayes (1995) does not conduct econometric analysis to support her research, her
discussion on the importance of self-esteem is tested in this thesis and this thesis expects
the lower the teenager’s self-esteem, the more likely the teenager will become pregnant.
2.2b. Family Dynamics
Dynamics of a teenager's family will also influence the behavior of a teenager
12
(Akerlof, Yellen, and Katz, 1996; Chandra et al 2008; Manlove et al., 2008: and
Oettinger, 1991). Oettinger (1991) looks at the relationship between enrollment of U.S.
teenagers during the 1970s in sex education in schools and their sexual behavior
following this education. He examines many variables to explain this relationship, which
is further explained later in this thesis, but specifically points out the importance of the
relationship between a teenager and their older sister. He estimates models that test if
enrollment in sex education affects sexual activity or pregnancy while controlling for
unobserved fixed family or community determinants. As previously mentioned, this
thesis expects that if a teen girl has an older sister with a child, they will be less likely to
becomes pregnant compared to a teen girl who does not have an older sister with a child.
This is because the teen without an older sister with a child does not fully understand the
hardship the older sister has faced.
The values a family places on sex, specifically on birth control and abortion, may
also play a role in teen behavior. Akerlof, Yellen, and Katz (1996) explain the linkage
between birth control, the legalization of abortion, and the declining rate of “shotgun
marriages,” which were conducted because the teenage daughter was pregnant and it was
historically socially unacceptable to have a child out of wedlock. By introducing both
birth control and allowing abortion to be legal, a shift in technology occurred and thus an
increase in choices about family planning. In their paper, a theoretical model shows that
the decreased cost of an abortion decreases the incentive to become engaged because now
that an abortion is available and being pregnant is no longer a concern, there is no reason
to get married. The relationship between teen pregnancy and family values is further
13
explored by Manlove, Ryan, and Franzetta (2008), who examine how group trends in
characteristics of the teenager’s family relationships, of the teenagers, and of the
relationship teenagers have with the opposite sex are all linked to trends in teenaged
reproductive health outcomes. They uses survey data from the 1992 National Survey of
Family Growth to identify how characteristics of the teenager's family, of the teenager,
and the relationships of a teenager are related with the transition to engaging in sexual
intercourse, which contraception to use when first engaging in sex, and the teenager
giving birth. Further, the data is in waves beginning with the first wave in 1992, second
wave in 1997, and the final wave in 2001. Manlove, Ryan, and Franzetta (2008) find
positive trends in teen pregnancy since the early 1990s due to changes in both family
relationships and family characteristics; as well as, changes within teenager relationships.
Factors associated with improvement in adolescent reproductive health include positive
changes within the family that includes increases in parental education and a reduced
likelihood of being born to a teen mother. They suggest the importance for teen programs
to take into account how family, individual, and relationship environments have some
bearing on a teenager's choice in engaging in sexual activity, contraception, and having
children.
This thesis, like Manlove, Ryan, and Franzetta (2008), estimate a logistic regression
using survey data that follows teenagers from eighth grade to after graduating high
school. Unlike Manlove, Ryan, and Franzetta (2008), this thesis does not include
teenaged males because it only looks at pregnancy and not the sexual activity of
teenagers. Similar to Manlove, Ryan, and Franzetta (2008) this thesis include family
14
characteristics, such as parents’ education, ethnicity, and relationships for analysis.
2.2c Television
One variable not included in Manlove, Ryan, and Franzetta (2008) is how television
influences teenager. Chandra et al (2008) includes television to evaluate how it shapes a
teenager's sexual views and behavior. She used data from the 1997 National Longitudinal
Survey of Youth national longitudinal survey, which followed teenage boys and girls
ages 12 through 17 years old for three years. A measure for viewing television containing
sexual content allows them to test if this programming leads to an increase in pregnant
teenage girls or a decrease in sexual responsibility for teenage boys. Chandra et al (2008),
like this thesis, uses logistic regression models. Their results indicate that teenagers who
watch television programs containing sexual content were two times as more likely to
become pregnant in the next three years than those that do not watch television programs
with any sexual content on television. Like Chandra et al (2008), this thesis examines the
relationship between how much television a teenager watches and teen pregnancy and
expects to see that with greater television viewing; the more likely the teenager will
become pregnant. Unlike Chandra et al (2008), this thesis separates weekday television
and weekend television since sexual content on television is more often on after 10pm
and on weekends.
2.2d Relationships with Others
Like the previous studies mentioned above, Oettinger (1991) also uses survey data,
the National Longitudinal Survey of Youth, which follows teenagers from the 1970s to
the early 1980s to look at the relationship between enrollment in sex education at school
15
and how sex education influences the hazard rates for engaging in sexual activity and
becoming pregnant. His theoretical model depicts a teenager’s decision to engage in
sexual activity and how that decision changes with changes in the type of sex education
program a teenager may experience. These changes in sexual activity are then translated
into changes in teen pregnancies. Oettinger (1991) introduces a variable that captures
whether a teenager has an older sister who has a child into his empirical analysis in
addition to including ethnicity and other variables mentioned in the above literature. He
shows having an older sister with a child will positively influence a teenager's behavior in
sexual activity. This pregnant older sister variable is included in this thesis as well, yet
expects a teenager is less likely to become pregnant if they have an older sister with a
child. Based on the models and assumptions, Oettinger (1991) finds enrollment in sex
education associated with a significant increase in the likelihood of engaging in sexual
activity for females and a smaller, and insignificant, increase in the likelihood of
becoming pregnancy. The effect of sex education was greater for teenage girls who had
minimal low cost alternatives for sex education information, such as Planned Parenthood.
The results suggest that sex education had some causal influence on teenagers engaging
in sexual activity, most likely this influence was from the type of information taught to
the teenagers, which changed the risks of sexual activity.
Unlike Oettinger (1991) this thesis does not include a sophisticated model to
consider different types of sex education. It will however measure the amount of sex
education but does not differentiate between the types of sex education that is taught,
such as abstinence-only sex education. In addition, Oettinger (1991) estimates models for
16
both teenage males and females by including the early teenage years in the analysis, and
by running simulations of various sex education policies to test the magnitudes of the
estimated effects of sex education. Where Oettinger (1991) investigates heterogeneity, he
does not addressing possible endogeniety, this thesis address the question of endogeniety.
Recall, it is possible that sex education programs were established to combat growing
teen pregnancy rates. This could complicate the econometric analysis of the data and is
tested in Chapter 4.
2.3 Closely Related Research
Kohler, Manhartt, and Lafferty (2008) estimate the effect of sex education on the
first time a teenager engages in sexual activity, and determine the risk of teen pregnancy
and spread of sexually transmitted diseases. They compare the risks of teenagers' sexual
health that had abstinence-only education and comprehensive sex education to those who
received no sex education at school. Some of the data collected includes demographics,
knowledge of sexual activity, thoughts and beliefs on family planning, and self reported
sexual activity, including previous sexually transmitted diseases. Analysis was restricted
to single, heterosexual teenagers from 15 to 19 years old who had either abstinence-only
sex education, comprehensive sex education, and no sex education. They considered
differences across gender but found none. In general, they found teenage girls who did
not have sex education tended to be the most likely to become pregnant. It was also
discovered that teenage girls who reported they had abstinence-only sex education were
no less likely to become pregnant than those with no sex education, Those who took
comprehensive sex education classes, however, were significantly less likely to become
17
pregnant than the other groups. This thesis examines many of the same variables as
Kohler et al. examine including rural and urban areas.
2.4. Summary
While many studies have been conducted about whether sex education should be
taught to teenagers and what should be included in the sex education courses, these
studies are missing analysis, which this thesis performs. Further this thesis includes:
1.testing for endogeneity, 2. determining the influence of sex education on the probability
that a teenager becomes pregnant, and 3. incorporating other influences into the analysis
such as the effect of television viewing on teen pregnancy. The following section
discusses the empirical model and data used in the analysis.
18
Chapter 3
EMPIRICAL MODEL AND DATA
Some studies, such as Oettinger (1991) and Kirby (1981), find sex education
offered in schools will reduce the teen pregnancy rate, but fail to address potential
endogeniety between teen pregnancy and sex education, calling the results of these
studies into question.
3.1 Empirical Model
For the analysis, a probit model is used. The use of a probit model allows for the
estimation of a model with a discrete dependent variable. The coefficients in the
regression results do not directly represent marginal effects. The coefficients do,
however, show the direction of the change. The reason they do not directly reflect
marginal changes is because any changes must be evaluated where all the other variables
in individual characteristics, family characteristics, and outside influences are held
constant at their means and are then transformed using the normal cumulative probability
distribution to determine the marginal effect. The average values are no longer
meaningful when so many of the variables are dummy variables, as they are in this thesis.
The dependent variable, HASACHILD, can take on one of two values. If the teen
girl becomes pregnant, the dependent variable would be one. If not, the dependent
variable would be zero. Therefore, consider the following equation:
(1.) HASACHILDij = β0 + β1(SEXED) +β2(INDIVIDUALij) + β3 (FAMILYij) + β4
(OUTSIDEij) + µij
19
where i= student identification
j= grade (8th, 10th, 12th)
HASACHILD includes teen girls who have a child. INDIVIDUAL is a vector of
individual reasons a teen girl becomes pregnant. FAMILY is a vector of family
characteristics that influence a teen girl in becoming pregnant. Finally, OUTSIDE is a
vector of outside influences that influence a teen girl in becoming pregnant. Note that the
i in the subscripts represents the individual student, i, and the j indicates which grade
student i is in when the data was taken. Thus, each student’s data appears three times
(once at each grade level) in the analysis.
Individual characteristics in this analysis include self-esteem and wanting a child.
Hayes (1995) explores whether a teen girl who feels she has high self-esteem is less
likely to become pregnant. This thesis also considers if a teen girl wants to have a child at
some point in her life, she is more likely to become pregnant as a teenager than a girl who
never wants to have a child or being uncertain if she wants a child someday.
Family characteristics include variables such as religious beliefs, relationships, and
education completed by parents, which might influence a teen girl’s probability of
becoming pregnant. The first variable considered is family income. Christopher and
Roosa (1990), East (1999a, 1999b), Kirby (2002a), and Oettinger (1991) suggest that a
teen girl’s probability of becoming pregnant is inversely related to family income. The
analysis also considers whether a teen girl’s older sister has a child affects the likelihood
of the teen girl will become pregnant. Oettinger (1991),Akerlof, Yellen, and Katz (1996),
and East (1999a, 1999b) expect if a teen girl has an older sister with a child, the teen girl
20
is more likely to become pregnant herself relative to those teen girls who do not have an
older sister with a child,. However, logic would suggest that teen girls with older sisters
would see the hardships their sisters have faced: no longer being able to spend time with
friends, high costs of daycare, diapers, and other supplies, and the lack of sleep when
having a baby. The younger sister may also see more long term consequences to having a
child such as dropping out of high school. Oettinger (1991) also suggests that the more
education a teen girl’s parents have, the less likely the teen girl will be to become
pregnant. That theory is investigated in this thesis as well. This thesis also investigates
the Oettinger (1991), Akerlof, Yellen, and Katz (1996), and Manlove (2008) suggestion
that the religion that a girl follows may affect her chances of becoming pregnant. The
data set used in this thesis, which is described in the next section, only permitted an
analysis of four religions: Presbyterian, Methodist, Lutheran, and Baptist. Finally,
whether different ethnicities are more likely to become pregnant is also explored.
Oettinger (1991) and Christopher and Roosa (1990) suggest Hispanics and African
Americans are more likely to become pregnant relative to other ethnicities.
Teen girls have other influences besides how they think and feel about
themselves, as well as, how their families beliefs and values. These other influences come
from the media, relationships outside of their family, the amount of alcohol they consume
in a year, and how active teen girls are in after school activities. Chandra et al (2008)
finds the more television a teenage girl watches, the more likely they will become
pregnant. This thesis evaluates television watching into two categories: amount of
television watched on weekdays and amount of television watched on the weekends. I
21
examine whether watching more television will make it more likely a teen girl will
become pregnant and the comparative relationship between pregnancy and watching
television on the weekends relative to watching television during the weekdays. Alcohol
consumption is another outside influence examined in the thesis. It is expected that the
more alcohol consumed, the more likely a teen girl will become pregnant. Finally, Kirby
(2002a) shows the more active a teenage girl is in after school activities, the less likely
she will become pregnant. This thesis includes religious activity as a school activity since
it is a similarly structured and chaperoned activity.
Preliminary work for this thesis attempted to evaluate the relationship between teen
pregnancy and the quality of the teen’s relationship with one of their teachers or other
adults outside of the family. Theoretically, this relationship could be important since
having a trusted adult other than a parent would allow for support and information a
parent may not give their child. This additional information would, in theory, help a teen
girl make better decision in their sexual activity, which can reduce the likelihood of
becoming pregnant. However, this variable had to be dropped from the analysis due to
collinearity. This is discussed in more detail in the next section.
Finally, this thesis includes the amount of sex education a teenage girl takes in school.
The starting assumption was that the more education a teen girl takes in school the less
22
likely she will become pregnant. This leads us to the following equation:
(2.) HASACHILDij = β0 + β1(SEMESTERSEXEDij) + β2 (WANTACHILDij) + β3
(SELFESTEEMij) + β1(FAMILYINCOMEij) + β2 (ETHNICITYij) + β3
(SISTERHASCHILDij) + β4(PARENTSEDUCATIONij) + β5 (RELIGIONij) + β6
(TVWEEKDAYij) + β7(TVWEEKENDij) + β8 (RELIOUSACTIVITYij) + β9
(ALCOHOLij) + µij
3.2 Data
As mentioned previously, the data used in this analysis are from the National
Educational Longitudinal Study of 1988 (NELS-88), a nationally represented
demographic survey providing trends in important changes which students deal with as
they attend middle school and high school. The NELS-88 data is a survey given every
two years starting in 1988 when the survey takers are in eighth grade with a final survey
given two years after high school graduation. Questionnaires ask a range of topics
including: school, work, and home experiences, educational resources and support,
education of their parents, neighborhood characteristics, educational and occupation
aspirations, and perceptions of the survey takers. This NELS-88 survey data were used in
this analysis because of the level of detail and the fact that the survey follows students
throughout their teen years, which is important to this thesis.
The surveys given ever two years were sent to teachers, parents, and students. The
survey had a sample size of 12,145 students. Students that dropped out of the survey were
replaced with new students. The base year of the NELS-88 survey is 1988. In this base
year, the student questionnaire captures basic background information and collects data
on a range of topics that include schoolwork, aspirations, social relationships, and data on
23
course offerings. The first follow up is in 1990 and collects data on the transition survey
takers make going from middle school to high school. This first follow up also asks
questions about students who drop out of school before the 10th grade, and on courses
being offered. The second follow up is in 1992 and collects data on courses being
offered, as well as, course grades and plans for after high school. There is a final follow
up in 1994, but is not included in this thesis because the survey takers were no longer
teenagers.
Not all of the participants in the NELS-88 study were used in this analysis. First, all
male participants were eliminated because males cannot become pregnant. Second, any
students that dropped out of the survey were not included in this analysis because it
becomes difficult to make any conclusions about students when so much data is missing.
Finally, any student that did not answer all the survey questions that were used in this
analysis was also eliminated because again, it becomes impossible to make any
conclusions about students without having all the available data. Therefore, the sample
size of data used in this analysis is 975 teen girls.
Because the NELS-88 survey captures changes teens go through, each wave has
specific questions that may not have always been asked in the other surveys. This means
some data is missing in each survey. In the base year, 1988, missing data was: if the
survey taker has a child, if the survey taker has an older sister with a child, if the survey
taker wants a child, and how much alcohol a survey taker drinks each year. This thesis
fills in the missing 1988 data with 1990 data for several reasons. First, the survey taker in
24
1988 is probably more similar to how they behave in 1990 than they are in 1992. Next,
the family is more likely to be similar to how they are in 1990 than they are in 1992.
Data missing in 1990 is family income and where they live, rural or urban area. Since
family income is only asked once, in 1988, 1988 data was used for 1990 and 1992.
Similarly, this analysis assumed a student and their families were more likely living in
the same place they lived in during 1988 instead of where they lived in 1992, so 1988
data was filled in for missing rural and urban data.
Finally, only two variables had missing data in 1992: Family income and how active
a survey taker was in participating in religious activities. Again, family income was only
asked during the base year, 1988, so this date was used for both 1990 and 1992 data.
1990 religious activity data was used as a proxy for the missing 1992 data.
NELS-88 data is categorical data, so all data were converted into dummy variables.
Because this thesis uses instrumental variables in the analysis, careful consideration was
made in selecting appropriate instrument variables. An instrumental variable must be
correlated with teen girls but uncorrelated with pregnant teens. Two such variables that
could be correlated with teen girls but uncorrelated with pregnant teen girls are URBAN
and REGION. URBAN classifies the urbanicity of a student’s school. This variable was
created directly from Quality Education Data. The U.S. Census uses these classifications.
Classifications reflect the sample school’s metropolitan status at the time of the 1980
decennial census. URBAN, in this survey, is classified as urban, suburban, and rural.
REGION indicates in which of the four U.S. Census regions the school is located. It was
created by recoding the sampled state of the eighth grade school into the four Census
25
Bureau regions.1 URBAN and REGION are both used in the 2SLS testing for
endogeniety. The following table, Table 3.1, shows where survey takers in this analysis
live.
Table 3.1: Instrument Variables
Instrument
Variables
8th Grade
10th Grade
12th Grade
5.0%
38.6%
39.7%
16.7%
5.0%
38.6%
39.7%
16.7%
5.0%
38.6%
39.7%
16.7%
26.2%
44.9%
28.9%
26.2%
44.9%
28.9%
28.1%
42.7%
29.2%
Region of US
NorthEast
NorthCentral
South
West
Urbanicity
Urban
Suburban
Rural
3.3 Descriptive Statistics
Because this thesis tries to answer whether sex education influences a teen girl
becoming pregnant, this section starts by looking at how much sex education survey
takers took in school. Table 3.2 show the amount of sex education survey takers received
at each wave.
1
The four regions are the Northeast (New England and Middle Atlantic states), the North Central (east
North Central and North West Central states), the South (south Atlantic, East South Central, and South
West Central States), and the West (Mountain and Pacific states).
26
Table 3.2: Sex Education by Grade
Amount of Sex
Education
8th Grade
None
81.9%
1 semester
18.1%
2 semesters
0.0%
3 semesters
0.0%
4 semesters
0.0%
10th Grade
62.5%
29.4%
7.0%
0.4%
0.7%
12th
Grade
24.9%
49.8%
15.3%
8.4%
1.5%
As seen in the table above, most 8th graders have not taken any sex education. By the
time the survey takers graduate, almost half of the survey takers have taken at least one
semester of sex education.
Table 3.3 shows the individual characteristics of the survey takers in each grade
and how they change each grade. In each grade most survey takers are uncertain if they
want a child.
Table 3.3: Individual Characteristics
Individual Characteristics
Want A Child
Yes
No
Maybe
Self-Esteem (I Don't Lack SelfEsteem)
Agree
Disagree
8th Grade 10th Grade
12th Grade
13.0%
36.3%
50.7%
13.0%
36.3%
50.7%
15.7%
25.4%
58.9%
92.1%
7.9%
90.7%
9.3%
90.8%
9.2%
With all of the hormone changes, pressures in and out of school with homework,
friends, and life after high school, seeing survey takers with who feel they do not lack
self-esteem is interesting because this would be a time when teenagers might doubt
themselves the most in appearance and grades.
27
Family characteristics, as seen in Table 3.4, show how families are also changing
from grade to grade. Because of the construction of the data, the family income variable
and the parents’ education variable do not change over time. Nor does ethnicity change
over time. Most of the survey takers in this analysis are Caucasian. Asian Pacific
Islander, American Indian, and Mixed are not included in the analysis because they are
collinear. Other family characteristic variables were not included because of collinearity
due to the assumptions made in the data from above. One of which is income ranges: $0,
less than $1,000, $1,000 to $3,000, $3,000 to $5,000, $5,000 to $7,000, $7,000 to
$10,000, $50,000 to $75,000, $75,000 to $100,000, and $100,000 to $200,000. The other
is parents’ education: Associate Degree, Bachelor Degree, and Masters Degree. Very few
sisters have a child and they increase slightly as the survey taker goes from 8th grade to
12th grade. This slight increase over time should not come as a surprise since the older
sisters are probably getting married and starting families since they are legal adults.
Those who are single have had more time to become pregnant out of wedlock. One large
surprise is the change in religion. Survey takers change from being Methodist to either
being Lutheran, Baptist, or Presbyterian.
Finally, Table 3.5 shows how outside influences change as each student goes from
8th grade to 12th grade. As the survey takers get older, they are watching slightly less
television during the weekdays and weekends; this could be that students have less time
as they get older since they may be participating in more after school activities, working,
or completing more homework. The survey takers are also starting to drive in 10th grade
and may be spending more time with their friends. Participation in religious activities
28
decreases as survey takers get older. This again may be because they are working,
choosing different after school activities to participate in, more homework to complete, or
since they can drive starting in the 10th grade, the survey takers may be spending more
time with their friends. Finally, as the survey takers get older they are drinking more
alcohol, but about half still do not drink at all during their teen years.
Table 3.4a: Family Characteristics- Income
8th
Income
Grade
5to10K
8.4%
10to15K
7.2%
15to20K
9.1%
20to25K
20.2%
25to35K
23.0%
35to50K
19.3%
50Kplus
12.8%
10th
Grade
8.4%
7.2%
9.1%
20.2%
23.0%
19.3%
12.8%
12th
Grade
8.4%
7.2%
9.1%
20.2%
23.0%
19.3%
12.8%
Table 3.4b: Family Characteristics- Sister Has A Child
8th
10th
12th
Sister Has A Child
Grade
Grade
Grade
Yes
0.0%
0.1%
1.4%
No
100.0%
99.9%
98.6%
29
Table 3.4c: Family Characteristics- Parents’ Education
8th
10th
Parents’ Education
Grade
Grade
No High School
Diploma
4.4%
4.4%
High School Diploma/
GED
16.9%
16.9%
Associates
38.2%
38.2%
Bachelors
19.9%
19.9%
Masters
12.1%
12.1%
Doctorate
8.5%
8.5%
12th
Grade
4.4%
16.9%
38.2%
19.9%
12.1%
8.5%
Table 3.4d: Family Characteristics- Ethnicity
8th
Ethnicity
Grade
Asian Pacific Islander
8.2%
Hispanic
8.4%
African American
5.2%
White
75.4%
American Indian
2.4%
Mixed
0.4%
10th
Grade
8.2%
8.4%
5.2%
75.4%
2.4%
0.4%
12th
Grade
8.2%
8.4%
5.2%
75.4%
2.4%
0.4%
Table 3.4e: Family Characteristics- Religion
8th
Religion
Grade
Baptist
9.5%
Methodist
63.5%
Lutheran
23.2%
Presbyterian
3.8%
10th
Grade
9.5%
63.5%
23.2%
3.8%
12th
Grade
21.7%
27.6%
34.2%
16.5%
30
Table 3.5: Outside Influences
Outside Influences
Television Watching (Weekday)
0 hours per day
less than 1 hour per day
1 to 2 hours per day
2 to 3 hours per day
3 to 4 hours per day
4 to 5 hours per day
over 5 hours per day
Television Watching (Weekend)
0 hours per day
less than 1 hours per day
1 to 2 hours per day
2 to 3 hours per day
3 to 4 hours per day
over 4 hours per day
Do You Participate in Religious
Activities
Yes
No
Alcoholic Drinks Consumed Per
Year
0
1-2
3-19
20+
8th
Grade
10th
Grade
12th
Grade
11.9%
30.7%
27.8%
16.7%
9.9%
0.0%
3.0%
19.8%
39.5%
20.2%
11.0%
4.1%
2.8%
2.7%
23.7%
35.3%
20.5%
11.0%
4.1%
2.8%
2.7%
6.5%
16.8%
24.6%
29.0%
23.1%
0.0%
10.8%
19.5%
21.4%
24.2%
17.4%
6.7%
10.8%
19.5%
21.4%
24.2%
17.4%
6.7%
98.7%
1.3%
58.3%
41.7%
58.3%
41.7%
100.0%
0.0%
0.0%
0.0%
62.4%
26.6%
10.8%
0.3%
52.0%
31.7%
15.5%
0.8%
31
Overall, the survey takers are not pregnant during their teen years, and most of them have
taken at least one semester of sex education before they graduate high school.
Additionally, most survey takers do not drink alcohol, feel they do not lack self-esteem,
but they do change their religion sometime between their 10th and 12th grade year. The
next chapter will supply the empirical analysis to understand the slight changes
particularly as they relate to teen pregnancy.
32
Chapter 4
EMPIRICAL ANALYSIS
The empirical model presented in the previous chapter is estimated using two
techniques. The first technique relies on an instrumental variable method to test, and, if
necessary, control for endogeniety of sex education. The second technique utilizes panel
data analysis to control for omitted factors that differ across grades, which affect students
similarly.
To address endogeniety, a two-stage least squares (2SLS) probit model is
estimated using URBAN and REGIONS as instrumental variables. Both URBAN and
REGION were chosen as instrumental variables in this analysis because teen girls live in
each area, rural, urban, and suburban, and they live in each of the four regions, but
pregnant teen girls do not necessarily live in each of these urban areas or in each region.
The result from the Hausman test shows no endogeniety exists between sex education
and teen pregnancy. Finally, because panel data is used in this analysis, a fixed effects
model can be estimated. The fixed effects control for differences across each grade that
affect all students similarly.
4.1 Baseline Probit Results
This analysis begins by discussing several results associated with the baseline
probit model, which does not incorporate grade-fixed effects. To begin with, sex
education taken at school, is only statistically significant at the one percent level. This
means, on average, girls who take sex education at school are less likely to become
33
pregnant relative to those teen girls who do not take any sex education in school. This
initially appears noteworthy, however, further analysis is necessary because this does not
take into account the differences across each grade that affect all students similarly as
seen later in the fixed effects model.
Turning to individual characteristics, as seen in Table 4.1a, the only variable
which is significant is WANTACHILD. WANTACHILD is statistically significant at the
five percent level. Further, it is slightly less likely a teen girl will become pregnant
relative to teen girls that do not want a child. This outcome appears to be illogical- if a
teen girl wants a child, it would seem the teen girl would be more likely to become
pregnant than teen girls who do not want a child. Upon further thought, however, this
outcome could be because teen girls are responding to the survey that was not specific
enough when asking when they wanted a child. If this is the case, then the survey taker
might have assumed the question was asking about wanting a child in the future, like
after high school, after college, or after marriage.
Results from family characteristics are very interesting, as seen in Table 4.1b with
the robust standard errors in parenthesis. This thesis expected the lower the family
income of a teen girl, the more likely she would become pregnant. In this analysis, the
two higher income ranges, $25, 000 to $35,000 and $35,000 to $50,000, are not
statistically significant at any level. The lowest income range, $5,000 to $10,000, is
statistically significant at the one percent level, while the next two income ranges,
$10,000 to $15,000 and $15,000 to $20,000, are statistically significant at the 10 percent
level. Interestingly, while only three incomes were statistically significant, they become
34
less significant as the family income decreases. Further, all the girls in families within
these income ranges which are statistically significant at either the one percent or the 10
percent levels are less likely, on average, to become pregnant relative to teen girls that
come from family incomes that are $50,000 and more. Perhaps teen girls from lower
income families are working so they have less time they can spend with their boyfriend
and thus less likely to become pregnant. Another interesting finding about family
characteristics is both levels of parents’ education- no high school diploma and high
school diploma/general equivalency exam (GED) - are statistically significant. Parents
without a high school diploma are statistically significant at the 10 percent level while
parents with only a high school diploma or a GED are statistically significant at a one
percent level. Further, teen girls whose parents’ do not have high school diploma, are on
average, less likely to become pregnant than teen girls whose parents have a doctorate.
Similar results are true for teen girls who have parents with either a high school diploma
or a GED. Overall, teen girls, regardless of their family income have about the same
likelihood of becoming pregnant.
All three religions, Baptists, Lutheran, and Methodist, are statistically significant
at the 10 percent level. Further, teen girls who are any of these religions are, on average,
about as likely to become pregnant as teen girls who are Presbyterian. This was
surprising since no religion encourages premarital sex, however, each religion has
different views on birth control. Methodists and Presbyterians view birth control as an
acceptable decision, however, Lutherans believe all forms of birth control are a sin.
35
Baptists believe birth control is a moral decision and birth control should be to prevent
conception not as a means to end a life.
Table 4.1a: Baseline Probit Results- Individual Characteristics
Probit Baseline
Regressors
Model
Sex Education
Want A Child
Not Sure If Teen Wants a Child
Have Good Self Esteem
Note: *1%, ** 5%, *** 10% significance level.
-0.2170 *
(.1270)
-1.1613 ***
(0.3255)
-0.2888
(0.3268)
0.1017
(0.4848)
36
Table 4.1b: Baseline Probit Results- Family Characteristics
Regressors
$5,000 - $10,000 (Family Income)
$10,000 - $15,000 (Family Income)
$15,000 - 20,000 (Family Income)
$20,000 - $25,000 (Family Income)
$25,000 - $35,000 (Family Income)
$35,000 - $50,000 (Family Income)
Older Sister Has a Child
Did Not Graduate High School
High School Diploma/ GED
Baptist
Methodist
Lutheran
Hispanic
African American
Note: *1%, ** 5%, *** 10% significance level.
Robust Standard Errors In Parenthesis
Probit Baseline
Model
-0.8666 *
(0.4818)
-1.1592***
(0.3986)
-0.9191***
(0.4175)
-0.8291 ***
(0.3648)
-0.4909
(0.3771)
-0.1378
(0.4617)
0.0312
(0.4102)
-0.7573 ***
(0.3344)
-0.4149 *
(0.2357)
1.1213 ***
(0.3841)
1.0071 ***
(0.2611)
0.9906 ***
(0.2681)
-0.3082
(0.2752)
-0.4552
(0.2869)
37
Table 4.1c: Baseline Probit Results- Outside Influences
Regressors
No Television Watched Per Weekday
Less Than One Hour Television Watched Per Weekday
1 to 2 Hours Television Watched Per Weekday
2 to 3 Hours Television Watched Per Weekday
3 to 4 Hours Television Watched Per Weekday
No Television Watched Per Weekend
Less Than One Hour Television Watched Per Weekend
1 to 2 Hours Television Watched Per Weekend
2 to 3 Hours Television Watched Per Weekend
3 to 4 Hours Television Watched Per Weekend
Religious Activity
No Alcoholic Drinks Per Year
1 to 2 Drinks Alcohol Per Year
3 to 19 Drinks Alcohol Per Year
Probit Baseline
Model
0.1735
(0.5331)
0.1342
(0.4824)
-0.4341
(0.4084)
-0.7911 *
(0.4553)
-0.9245 ***
(0.4511)
-5.1132 ***
(0.4072)
-4.8762 ***
(0.4672)
-4.4976 ***
(0.5675)
-4.6309 ***
(0.5007)
-4.0896 ***
(0.4177)
0.2096
(0.2236)
-3.7394 ***
(0.3740)
-3.1757 ***
(0.4689)
-3.8885 ***
(0.4010)
Note: *1%, ** 5%, *** 10% significance level.
The results for the outside influences, in Table 4.1c, were most in line with
expectations. This thesis expected the more a teen girl watched television, particularly on
the weekends, the more likely she would become pregnant. To begin, only television
watched on the weekends and television watched two or more hours during the weekdays
38
are statistically significant. Teen girls who watch television two to four hours a week are
less likely to become pregnant compared to teen girls who watch five or more hours of
television during the week. Further, teen girls who watch zero to four hours of television
during the weekend are, on average, less likely to become pregnant as teen girls who
watch five or more hours of television during the weekends. Therefore, it appears that the
more television a teen girl watches the more likely she will become pregnant, and
particularly if the teen girl is watching television on the weekends.
Finally, teen girls who either do not drink any alcohol in a year or drink up to 19
alcoholic drinks a year are less likely to become pregnant as teen girls who drink more
than 19 alcoholic drinks a years. This is not a surprise as alcohol can impair judgment.
Some of the results were consistent with expectations, while other results were
not which suggests there may be some omitted variable bias. The baseline probit model
did not address if sex education is endogenous. The next section addresses this concern
with a 2SLS model.
4.2: Test of Endogeneity- 2SLS
As previously mentioned, sex education may be an endogenous variable. To test
this hypothesis, a 2SLS model is used. The first stage regresses sex education on the
exogenous variables and the instrument variable. Then, the residual from the first-state
regression is included as an additional regressor in the second-stage. By including the
residual from the first-stage regression, a Hausman test of endogeneity can be performed
at the same time by evaluating the significance of the coefficient of the residual from the
39
first-stage. Specifically, should the efficient of the residual be statistically significant,
then sex education is endogenous. If not, sex education is exogenous.
Table 4.2a: Test for Endogeneity- Individual Characteristics
Regressors
Sex Education
Want A Child
Not Sure If Teen Wants a Child
Have Good Self Esteem
Note: *1%, ** 5%, *** 10% significance level.
Robust Standard Errors In Parenthesis
Second- Stage
Least Squares
(Test for
Endogeneity)
-0.2325
(0.1259)
-1.1745 ***
(0.3236)
-0.3145
(0.3291)
-0.4951
(0.5099)
40
Table 4.2b: Test for Endogeneity- Family Characteristics
Regressors
$5,000 - $10,000 (Family Income)
$10,000 - $15,000 (Family Income)
$15,000 - $20,000 (Family Income)
$20,000 - $25,000 (Family Income)
$25,000 - $35,000 (Family Income)
$35,000 - $50,000 (Family Income)
Older Sister Has a Child
Did Not Graduate High School
High School Diploma/ GED
Baptist
Methodist
Lutheran
Hispanic
African American
Note: *1%, ** 5%, *** 10% significance level.
Robust Standard Errors In Parenthesis
Second- Stage
Least Squares
(Test for
Endogeneity)
-0.7682
(0.4736)
-1.1065 ***
(0.3868)
-0.8250 ***
(0.4101) ***
-0.7901***
(0.3657)
-0.4537
(0.3745)
-0.0594
(0.4808)
0.0419
(0.4198)
-0.8453 ***
(0.3546)
-0.4489 *
(0.2419)
1.1665 ***
(0.3674)
1.2256 ***
(.3805)
1.085 ***
(.3195)
-0.3578
(0.3015)
-0.3681
(0.2849)
41
Table 4.2c: Test for Endogeneity- Outside Influences
Regressors
No Television Watched Per Weekday
Less Than One Hour Television Watched Per Weekday
1 to 2 Hours Television Watched Per Weekday
2 to 3 Hours Television Watched Per Weekday
3 to 4 Hours Television Watched Per Weekday
No Television Watched Per Weekend
Less Than One Hour Television Watched Per Weekend
1 to 2 Hours Television Watched Per Weekend
2 to 3 Hours Television Watched Per Weekend
3 to 4 Hours Television Watched Per Weekend
Religious Activity
No Alcoholic Drinks Per Year
1 to 2 Drinks Alcohol Per Year
3 to 19 Drinks Alcohol Per Year
error term
Note: *1%, ** 5%, *** 10% significance level.
Second- Stage
Least Squares
(Test for
Endogeneity)
0.3672
(0.4828)
0.2985
(0.5128)
-0.2016
(0.5145)
-0.5289
(0.5290)
-.5253
(0.6919)
-4.9729 ***
(0.6393)
-4.7189 ***
(0.6348)
-4.2805 ***
(0.6036)
-4.4945 ***
(0.6625)
-3.832 ***
(0.5293)
0.7617
(.8960)
-3.377 ***
(0.4903)
-3.3390 ***
(1.0947)
-4.048 ***
(1.0367)
1.007
(1.622)
42
As seen in Table 4.2c, the residual coefficient is not statistically significant at any
level and therefore, sex education is not endogenous. As seen in the baseline probit
results, WANTAKID is statistically significant and still at the 10 percent level, which
means a teen girl is less likely to become pregnant relative to girls who do not want a
child. The same reasons why a teen is less likely to become pregnant as in the baseline
probit results remain for this result.
Turning to family characteristics, the only difference between the 2SLS results
and the baseline probit result is the lowest family income range, $5,000 to $10,000 is now
statistically significant at the 10 percent level. This further proves that teen girls from
lower income families are less likely to become pregnant, on average, relative to families
with incomes greater than $50,000. There were no changes in the statistical significance
level in all the ethnicities.
Outside influences, however, did have some interesting changes. In the 2SLS,
only television watched on the weekends is statistically significant, and all amounts of
watching television is statistically significant at the 10 percent level. This further shows
the teen girls that watch no television on the weekends to less than 5 hours are less likely
to become pregnant relative to teen girls who watch 5 hours or more television on the
weekends. Overall, the less a teen girl watches television on the weekends, the less likely
she will become pregnant. This may have something to do with the shows that are
televised. Finally, like in the baseline probit model, teen girls that drink less than 20
alcoholic drinks in a year are less likely to become pregnant than teen girls who drink 20
or more drinks in a year. Again, this is no surprise as alcohol can impair judgment.
43
Finally, because the coefficient on the error term is not statistically significant at
any level, sex education is not endogenous. Because sex education is not endogenous, the
analysis can now apply the fixed effects technique to control for all changes that affects
students similarly as seen in the next section.
4.3: Grade Fixed Effects
Because this analysis uses panel data and may have omitted variable bias, as seen
in the baseline probit model results, using fixed effects can address some of this bias. By
using grade fixed effects, this analysis will be able to control for changes over each grade
that affect all students similarly. These changes can be in maturity and hormones to name
a few. It is expected that as each teen girl advances, she will have more knowledge which
will lead her to make more informed decisions.
Table 4.3a: Fixed Grade Effects Model Results- Individual Characteristics
Probit Fixed
Regressors
Effects Model
Sex Education
Want A Child
Not Sure If Teen Wants a Child
Have Good Self Esteem
Note: *1%, ** 5%, *** 10% significance level
0.1206
(0.1179)
-1.2340 ***
(0.3432)
-0.4370
(0.3711)
-0.3383
(0.5617)
44
Table 4.3b: Fixed Grade Effects Model Results- Family Characteristics
Probit Fixed
Regressors
Effects Model
$5,000 - $10,000 (Family Income)
-0.7206
(0.51601)
$10,000 - $15,000 (Family Income)
-1.1935 ***
(0.4681)
$15,000 - 20,000 (Family Income)
-0.8701 *
(0.4523)
$20,000 - $25,000 (Family Income)
-0.8806 ***
(0.3866)
$25,000 - $35,000 (Family Income)
-0.4351
(0.4250)
$35,000 - $50,000 (Family Income)
-0.0637
(0.5163)
Older Sister Has a Child
0.1317
(0.4583)
Did Not Graduate High School
-0.5650
(0.3834)
High School Diploma/ GED
-0.4708 *
(0.2682)
Baptist
1.1290 ***
(0.4201)
Methodist
0.5803 ***
(0.2908)
Lutheran
0.7141 ***
(0.2649)
Hispanic
-0.3157
(0.2887)
African American
-0.3703
(0.3407)
Note: *1%, ** 5%, *** 10% Statistical Significance
Robust Standard Errors In Parenthesis
45
Table 4.3c: Fixed Grade Effects Model Results- Outside Influences
Probit Fixed
Regressors
Effects Model
No Television Watched Per Weekday
0.3409
(0.5628)
Less Than One Hour Television Watched Per Weekday
0.2625
(0.5596)
1 to 2 Hours Television Watched Per Weekday
-0.4211
(0.4788)
2 to 3 Hours Television Watched Per Weekday
-0.7202
(0.5413)
3 to 4 Hours Television Watched Per Weekday
-1.4749 ***
(0.5605)
No Television Watched Per Weekend
-5.508 ***
(0.3830)
Less Than One Hour Television Watched Per Weekend
-5.2519 ***
(0.3245)
1 to 2 Hours Television Watched Per Weekend
-4.7556 ***
(0.3658)
2 to 3 Hours Television Watched Per Weekend
-4.9158 ***
(0.2740)
3 to 4 Hours Television Watched Per Weekend
-4.1754 ***
(0.3153)
Religious Activity
-0568
(0.2098)
No Alcoholic Drinks Per Year
-4.5057 ***
(0.4025)
1 to 2 Drinks Alcohol Per Year
-3.6516 ***
-(0.3214)
3 to 19 Drinks Alcohol Per Year
-4.3400 ***
(0.4415)
I.grade_10
5.0600 ***
(.3663)
I.grade_12
6.1294 ***
(0.4305)
Note: *1%, ** 5%, *** 10% Statistical Significance
To begin, the fixed grade effects model controls for differences over each grade
that affect all students in the same way, both the 10th grade and the 12th grade are
46
statistically significant at the ten percent level. On average, teen girls in the 10th grade are
more likely to become pregnant than teen girls in the 8th grade and teen girls in the 12th
grade are more likely to become pregnant than teen girls in the 8th grade.
Once again, teens who want a baby are statistically significant at the ten percent
level, however, they are less likely to become pregnant compared to those teens who do
not want a child. The same reasoning in the baseline probit model is used to explain this
relationship. Family income also has ranges that are statistically significant at the one and
ten percent level. Family income range $15,000 to $20,000 is statistically significant at
the one percent level, while family ranges $10,000 to $15,000 and $20,000 to $25,000 are
statistically significant at the ten percent level. Similar to the baseline probit results, the
teen girls from lower incomes are not as likely to become pregnant and teens that come
from higher income families. Also like the baseline probit model, none of the ethnicities
are statistically significant at any level. This did not match expectations since this thesis
expected Hispanics and African Americans teen girls to be more likely to become
pregnant than any other ethnicity. Further, like the baseline probit model, all of the
religions are statistically significant at the ten percent level. A teen girl who is Baptist,
Lutheran, or Methodist is more likely to become pregnant than teen girls who are
Presbyterian. This relationship continues to be a surprise result.
Finally, the outside influence variables are least surprising since they fall in line
with expectations and are consistent with the baseline probit model. We can see that all
amounts of alcohol are statistically significant at the ten percent level. Again, like the
probit model, it shows drinking zero to no drinks a year will reduce a teen’s likelihood of
47
becoming pregnant relative to teen girls that drink 20 or more drinks a year. This is still
not a surprise, because alcohol impairs judgment. Additionally, like the baseline probit
model, watching television is statistically significant. Teen girls that watch three to four
hours of television on weekdays are less likely to become pregnant than teens that watch
five or more hours of television during the weekdays at the one percent statistical
significance level. Teen girls that watch any television up to four hours during the
weekend are much less likely to become pregnant than teen girls who watch more than 4
hours of television on the weekends. This again is in line with the baseline probit model,
teen girls that watch less television, particularly on the weekends, are less likely to
become pregnant than teen girls that watch a large amount of television. Similar to the
baseline probit model, the only parents’ education level that is statistically significant are
parents’ with a high school diploma/GED. This level of parents’ education is statistically
significant at the one percent level. Further, the teens whose parents only have a high
school diploma or GED are less likely to become pregnant relative to teens whose parents
have a doctorate.
Despite the fact that some of the results did match the expectations, some did not
and thus there are some interesting results. The first interesting result is the relationship
between religion and teen pregnancy. Based on the beliefs of Baptists, Lutherans,
Methodists, and Presbyterians, teens that follow their faith should be less likely in
becoming pregnant, not as likely. Another interesting result is the inconclusive
relationship between an older sister having a child and teen pregnancy. The literature
suggested a positive relationship, I suggested a negative relationship, and no relationship
48
could be established based on the results of this analysis.
49
Chapter 5
CONCLUSION
This thesis investigates the relationship between sex education and teen
pregnancy. This thesis also addresses concerns of endogeniety, and considers differences
between grades that influence all students similarly
To accomplish these tasks, I first test for endogeniety using a 2SLS model and a
Hausman test for endogeniety. Because the error term was not significant at any level, no
endogeniety exists, As such, the analysis proceeds by conducting panel data analysis
involving grade fixed effects. By using fixed effects, the analysis controlled for
difference over each grade that affects all the students in the same manner. The results
from this latter analysis shows no statement can be made regarding whether sex
education causes teen pregnancy or if educating teens reduces the teen pregnancy rate.
Other statements can be made about variables that influence the probability a
teenage girl becomes pregnant. First, monitoring how much television is being watched
particularly on the weekends may lead to fewer pregnancies. Also, closer supervision
over alcohol consumption may lead to fewer pregnancies. Not only is underage drinking
illegal, it can increase the likelihood of a teen girl becoming pregnant. Next, because teen
girls that are affiliated with being Baptist, Methodist, Lutheran, and Presbyterian were all
equally likely to become pregnant, these churches should reevaluate the messages they
are sending about premarital sex and birth control which may lead to fewer pregnancies.
50
To further this research, more current data could be used instead of the NELS-88
data. By using up-to-date information, not only will there be a more current
understanding of what influences a teen girl in becoming pregnant so teen pregnancy
rates will decline once again, but this can also be applied to reducing teens afflicted with
sexually transmitted diseases.
51
REFERENCES
Akerlof, George A., Michael L. Katz, and Janet L. Yellen. "An Analysis of Out-ofWedlock Childbearing in the United States." Quarterly Journal of Economics
11.2 (1996): 277-317. Print.
Chandra, Anita, Steven C. Martino, Rebecca L. Collins, Marc N. Elliott, Sandra H. Berry,
David E. Kanouse, and Angela Miu. Pediatrics 122.5 (2008): 1047-054. Print.
Christopher, F., and M. Roosa. "An Evaluation of an Adolescent Pregnancy Prevention
Program: Is `just Say No' Enough?" Family Relations 39 (1990): 68-72. Print.
East, P. L. "Past Physicial Abuse Is Related to Pregnancy as an Adolescent." Journal of
Pediatric and Adolescent Gynecology 12.3 (1999): 133-38. Print.
East, P. L. "The Younger Siblings of Teenage Mothers: a Follow-up of Their Pregnancy
Risk." Development Psychology 37.2 (1999): 254-64. Print.
Hayes, Irene. "Sex Education in the Early Year." Health Education 95.1 (1995): 22-27.
Print.
Kirby, and Scales. "Enhancing Ethical Decision Making in Sexuality and AIDS
Education." Family Relations 30 (1981): 229-37. Print.
Kirby, D. "Effective Approaches to Reducing Adolescent Unprotected Sex, Pregnancy,
and Childbearing." Journal of Sex Research 39.1 (2002): 27-33. Print.
Kirby, D. "Understanding What Works and What Doesn’t in Reducing Adolescent
Sexual Risk-taking." Family Planning Perspectives 33.6 (2001): 276-81. Print.
52
Kirby, Douglas. "Evaluating Sexuality Education Programs." Indpendent School 41
(1981): 105-14. Print.
Kohler, P. K., L. E. Manhart, and W. E. Lafferty. "Abstinence-Only and Comprehensive
Sex Education and the Initiation of Sexual Activity and Teen Pregnancy." Journal
of Adolescent Health 42.4 (2008): 344-51. Print.
Macdonald, D. I. "An Approach to the Problems of Teenage Pregnancy." Health Report
102.102 (1987): 377-85. Print.
Manlove, J., S. Ryan, and K. Franzetta. "Older Sexual Partners During Adolescence:
Links to Reporductive Health Outcomes in Young Adulthood." Perspectives on
Sexual and Reporductive Health 44.5 (2008): 413-23. Print.
Oettinger, Gerald S. "The Effects of Sex Education on Teen Sexual Activity and Teen
Pregnancy." Journal of Political Economy 107.9 (1991): 606-35. Print.
Planned Parenthood. 2009. Web. 01 Dec. 2010. <http://www.plannedparenthood.org/>.