Soc 971 Week 5: Cohabitation
February 16, 2006
Data and Methods
Prepared by Nikki and Hongyun
Data Sources

Until the late 1980s, researchers used indirect estimates of cohabitation prevalence (e.g., the
Census Bureau’s POSSLQ estimates)

1987-88 NSFH collected the first cohabitation histories. The dataset includes complete
cohabitation histories from a sample of men and women at all ages, over-sampling currently
cohabitated men and women.
- Includes data on cohabiters’ marriage plans, the nature and quality of the relationship between
partners, and attitudes relating to marriage and cohabitation

In 1990, the census began to include the category “unmarried partner” as a possible response to
the household relationship question. In 1995, the Current Population Survey (CPS) began to
include the “unmarried partner” category as well.

In 1995, the National Survey of Growth (NSFG) began collecting detailed information about
cohabitation.
NSFG-5 is a periodic survey conducted by the National Center for Health Statistics with the
primary goal of providing estimates of actors affecting the US birth rates and the reproductive
health of US women 15-44. Cycle-5 provides complete cohabitation histories. It interviewed
10,847 respondents over the first months of 1995.

Longitudinal Study of the High School Class of 1972 (1972-86) (Brien, Lillard& Waite 1999)

Marital Instability Over the Life Course (1980,1992,1997,2000) (Dush, Cohan&Amato 2003)
Measures

Indirect vs. Direct Methods

POSSLQ: Partners of the Opposite Sex Sharing Living Quarters
- Developed by researchers at the Census Bureau in the late 1970s
- Indirect measure based on household composition
- POSSLQ households are those that contain two and only two adults (age 15+) who are
unrelated and of the opposite sex
Limitations of traditional POSSLQ measure:
-
Includes adults who live together as roommates, not couples
Excludes cohabiters who share households with other adults
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-
Excludes households with own children or other relatives age 15 or older
“Adjusted POSSLQ” measure (Casper & Cohen 2000)
- CPS data
- Does not exclude households with multiple related adults (many of these related adults are
15- to 17-year-old children of one member of the cohabiting couple)
Definition: Adjusted POSSLQ households contain:
1. A reference person (householder)
2. One other adult (age 15+) of the opposite sex who is not in a related subfamily, not a
secondary individual in group quarters, and not related to or a foster child of the reference
person
3. No other adults (age 15+) except foster children, children or other relatives of the reference
person, or children of unrelated subfamilies
Casper and Cohen (2000) compared Adjusted POSSLQ estimates to traditional POSSLQ
estimates and new direct estimates. They found that the Adjusted POSSLQ represents an
improvement over the traditional POSSLQ for estimating historical trends in cohabitation. The
traditional POSSLQ measure underestimated cohabiters among middle-aged persons, those
who were divorced or separated, and those with children.
Direct estimates of cohabitation rates from the NSFH and NSFG (Bumpass & Lu 2000) are
higher than the CPS indirect measures (see Casper & Cohen 2000 for discussion of possible
reasons). However, the Adjusted POSSLQ produces relatively unbiased estimates of the
characteristics of cohabiters.

Cohabitation rates:
- Percentage of all adults who are cohabiting
- Percentage of all unmarried persons who are cohabiting
- Percentage of all persons in unions who are unmarried
Estimates of the prevalence of cohabitation may vary greatly depending on which rate is
calculated. Example: racial differentials in cohabitation rates (and marriage rates)

Cohabitation among same-sex couples – measurement challenges:
-
Estimates vary by the time frame and the measure used to identify sexual orientation
Possible misreporting of relationship status
Sample sizes of most national surveys that ask about sexual orientation are not large enough
to obtain reliable estimates of same-sex cohabiting couples. Only the decennial census can
provide these estimates.
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Methods
Quantitative

Period Cox model and multivariate hazard model.
(Bumpass & Lu2000, Bumpass and Raley1995, Bumpass, Sweet and Cherlin 1991)
To estimate the children’s family experience, using women’s cohabitation histories:
Percentage of births to unmarried mothers and cohabiting mothers
Relative risk of transition into cohabiting family for children before age 16.
Expected percentage of childhood yeas spent in cohabitation, marriage or single-mother
families

Continuous time-hazard models
(Brien, Lillard& Waite 1999; Lillard, Brien and Waite 1995)
In order to examine the interrelation of entry into marriage, entry into cohabitation, and
nonmarital pregnancy, the author
Assume that each event may occur multiple times over the period of observation for any
particular women; the outcome of one process may influence the risk of another event
or the risk of a repetition of the same event.
Construct a model for the timing of each occurrence of the event, while at risk, is a
continuous-time failure-time process represented by a hazard equation.
Dependent variables are hazard of beginning a event;
Explanatory variable include Time/Duration, previous relationship, presence of
Children, education and background information.

Regression analysis ( OLS regression for continuous marital quality and Logistic regression
for dichotomous divorce)
(Dush, Cohan&Amato 2003)
In order to test the selection and experience of cohabitation perspective in explaining the
relation between premarital cohabitation and marital dysfunction, the authors conducted two
regression analysis.
Dependent variable: (1) continuous Marital quality was measured by marital happiness
and marital conflict; (2) Dichotomous Divorce
Explanatory variable: (1) Selection factors, including race, parental divorce, marriage
order, education, family income and welfare use. (2) Control variable include gender,
age, and duration
Qualitative

Interview (Smock, Manning and Poter 2003)
In order to examine how the economic consideration shape the decision of marriage among
cohabiters, the authors conducted semi structured in-depth interviews with 115 young adults
who were currently cohabiting or had recently cohabited in 2002. The authors classified the
attitudes into five groups of consideration. The respondents lie 18-36 age intervals,
representative as working and lower middle class.
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