SOME SELECTED FINDINGS OF THE PRINCETON
FERTILITY STUDY: 1963
CHARLES F. WESTOFF,1 ROBERT G. POTTER,2 AND PHILIP C. SAGP
RESUMEN
Deepues de tres anos se hizo una reencuesta de una muestra probabilistica de respondientes que
al principio vivian en siete de las areas metropolitanas mas grandes de los Estados Unidos y que
habian tenido el segundo hijo seis meses antis de la primera entrevista. Se encontr6 en la encuesta
anterior que la efectividad de la contraconcepcion fue comparativamente baja entre el casamiento y
elnacimiento del primer hijo, y no mejor6 grandemente entre el primero y segundo hijo. La reencuesta
revel6, sin embargo, que despues del nacimiento del segundo hijo la eficiencia de la contraconcepcion
mejor6 fuertemente. Los autores llegan a la conclusi6n de que el control de nacimientos se practica
primordialmente para espaciarlos en los primeros anos dematrimonio y conuna eficiencia comparetivamente baja. A medida que las parejas alcanzan el tamano deseado de familia la efectividad de su
practica anticoncepcional aumenta fuertemente. La encuesta explor6 una iez mas una amplia eerie
de hypotesis relativas a factores sociales y psicol6gicos vinculados a la fecundidad. Se encontr6 que la
religi6n es un factor importante. Los Cat6licos que han asistido a eecuelos de la iglesiaespecialmente
collegios tendian a mostraruna fecundidad mayor quelos otros. Se encontr6 que la variable categoria
socio-econ6mica tenia una correlaci6n baja con la fecundidad, y que la correlaci6n era positiva para
los Cat6licos y negativa para los Protestantes. La movilidad social no [ue relacionada con la fecundidad. Los resultados completos del estudio se presentan en un monografia El TercerHijo publicada
porla Princeton Press. Los autores estanpreparando una tercera entrevista para la muestra referida.
Thus far two volumes reporting the
results of the so-called Princeton Fertility Study have been published-Family
Growth in Metropolitan America 4 and The
Third Child.5 The analyses of both volumes have been directed toward two
main objectives. The first is to examine
the degree to which the number and spacing of births is controlled by fertility preferences-that is, desired family size and
spacing preferences-with an accompanying effort to learn more about the means
and barriers to such control. Secondly, a
broad range of social and psychological
factors have been considered for their
ability to discriminate, both individually
and jointly, selected measures of birth intervals, desired family size, family-planning success, and fertility three to four
1 Office of Population Research, Princeton
University.
2 Brown University.
3 University of Pennsylvania.
• C. F. Westoff, R. G. Potter, Jr., P. C. Sagi,
and E. G. Mishler, Family Growthin Metropolitan
America, Princeton, Princeton University Press,
1961.
5 C. F. Westoff, R. G. Potter, Jr., and P. C.
Sagi, The Third Child, Princeton, Princeton University Press, 1963.
130
years after the second child. In the present review, results will be presented as a
series of propositions grouped around the
two major interests just outlined.
The original probability sample of 1165
respondents represented couples having a
second birth in September of 1956, six
months before the first interview, and who
were at the time residing in one of the
seven largest Standard Metropolitan Areas
of the United States. The respondents are
further delimited by being native-white
and English-speaking with marital histories uncomplicated by divorce, permanent separation, death, or extensive pregnancy wastage. The group reinterviewed
three years later (1960) is smaller-90S
compared to 1165-mainly because of
difficulties encountered in relocating couples and because of refusals.
A number of our results may be viewed
as replications on a more specialized sample of findings from the 1955 Growth of
American Families Study" of Freedman,
Whelpton and Campbell including generS Ronald Freedman, P. K. Whelpton and Arthur Campbell, Family Planning, Sterility, and
Population Growth, McGraw-Hill, New York,
1959.
Some Selected Findings of the Princeton Fertility Study: 1963 131
alizations relating to age of first marriage,
consensus on the desirability of two to
four children, and the relationship between first use of contraception and pregnancy interval. The birth spacing observed, combined with the young ages at
marriage and preferences for two, three,
or four children means that most couples
attain desired family size while still in
their late twenties or early thirties and, as
a result, face a "risk period"-perhaps
averaging ten or more years to menopause-during which they must practice
highly effective birth control if they are
to limit their families to desired size.
Another finding consistent with their
results is the low effectiveness of contraception practiced during the first two
birth intervals-a time when nearly all
couples are practicing contraception to
postpone rather than to prevent pregnancies. Nor did contraception seem to
become more effective as one proceeded
from the first to the second interval.
This lack of improvement is puzzling.
Given youthful ages at marriage and preferences for two, three or four children,
such ineffective contraception projected
over entire reproductive periods implies
an average of at least two excess pregnancies per couple. Yet data from other
sources plainly belie this projection. In
particular, about three-quarters of the
"relatively fecund" wives aged 35-39
from the Freedman, Whelpton and Campbell study claimed to have successfully
limited the number of their pregnancies.
Even though these claims might be somewhat exaggerated, a high enough caliber
of family limitation was indicated so that
one wondered if effectiveness of contraception did not improve later in marriage
when being used to prevent unwanted
pregnancies rather than merely to space
desired ones. Lacking this explanation,
one could only posit wholesale reliance
upon sterilization and induced abortion.
While the Freedman, Whelpton and
Campbell study had shown sterilization
to be an important element, the incidence
indicated could not suffice as the explanation. Nor does it seem plausible to view
induced abortion as the primary means of
family limitation in this country.
A reanalysis of the contraceptive experience of the first two birth intervals, together with an analysis of contraceptive
experience following second birth, has led
to altered conclusions about the trend of
contraceptive effectiveness with increasing marriage duration. By considering
only the first 12 months of experience in
any birth interval, and recomputing rates
of accidental pregnancy on this basis, it is
revealed that the fraction of high-risk
couples practicing ineffectual contraception is definitely higher in the first interval
following marriage than in the interval
followingfirst birth. The incidence of early
accidental pregnancy continues to decline
when one proceeds to the interval following the second birth. Even more striking,
however, is the relationship between contraceptive effectiveness and the number
of additional children desired which leads
to the following proposition:
As couples approach desired family
size, the effectiveness with which they
practice contraception increases sharplyso much so that this improved contraception would appear to be the main factor
in the family limitation being attained in
this country. A more decisive confirmation
of this proposition will be achieved when
the sample is interviewed again after additional experience.
As a consequence of this relationship,
studies not distinguishing between contraception used for family limitation and
contraception used for spacing are likely
to underestimate the Ultimate use-effectiveness of a given method. By the same
token a comparison of two methods based
on experience from a single birth interval
will be biased if the users of one method
are nearer their family-size objectives
than users of the other. A case in point is
the rhythm method, favored by Catholics,
as opposed to the presumably more effective mechanical-chemical methods favored by Protestants and Jews because
132 DEMOGRAPHY
the latter prefer fewer children on the
average than do Catholics.
The improvement in contraceptive control with increasing marriage duration is
clearly not a matter of couples shifting
from ineffective to effective methods of
contraception in as much as the composition of methods used after the second
birth is much the same as that between
marriage and first birth. Moreover, the
predominantly young ages of the wives
preclude sharply declining fecundity as an
explanation. Nor has any association
been found between reported coital frequency and contraceptive effectiveness.
In addition, there does not appear to be
any important practice effect, wherein
contraceptive skill increases with longer
usage, since the relationship between
effectiveness of contraception and desired
number of additional children remains
strong among couples practicing contraception for the same number of intervals.
Rather the chief mechanism in the improvement of contraception appears to be
an increased regularity of practice.
The present study is the first to investigate how much couples know about the
location of the fertile period within the
monthly cycle and the relevance of this
knowledge for contraception. There is
considerable variation in the extent and
accuracy of women's knowledge of the
ovulatory cycle. Only half of the women
had the correct information by any liberal
interpretation. Knowledge about the timing of ovulation in the monthly cycle,
however, does not appear to influence
efficiency with contraception, except
among those using the rhythm method.
Wife's desired family size six months
after the second birth has proved to be
the best single predictor of fertility over
the next three years of all the data collected in the first interview. Several reasons for this are: her desired family size
is found to remain rather stable (the correlation between desires expressed at the
beginning and at the end of the three-year
interval is .70), corroborating a result
from a Detroit Area Study;' husband and
wife's desires are similar (correlation .66):
and contraception becomes more effective
once desired family size is attained, so
that relatively few of those desiring two
children have an unwanted third birth.
Contributing to the inverse correlation
between length of birth intervals and completed family size, so thoroughly documented by Glass and Grebenik for Great
Britain" and more recently by the Census
Bureau for the United States," is the inverse correlation between length of birth
intervals and desired family size. Familysize preferences are linked to birth spacing chiefly in two ways. Wives desiring
larger families tend to plan shorter birth
intervals as evidenced by more non-use of
contraception for reason of wanting another pregnancy as soon as possible and
by earlier interruption of contraception
after marriage or a childbirth. At the same
time, wives desiring more children tend to
practice less efficient contraception and
more often forego use of it for reasons unrelated to spacing objectives.
The average length of the first two
birth intervals has proven the strongest
predictor, after desired family size, of the
number of pregnancies during the three
and one-half year period following the
second birth. The predictive power depends on multiple bases, such as the positive correlation of consecutive conception
delays, as well as the tendencies of couples
desiring large families to seek shorter birth
intervals than average and to practice
contraception more casually during the
initial birth intervals.
7 David Goldberg, Harry Sharp, and Ronald
Freedman, "The Stability and Reliability of Expected Family Size Data," Milbank Memorial
Fund Quarterly, October, 1959, pp, 369-85.
8 D. V. Glass and E. Grebenik, The Trend and
Pattern of Fertility in Great Britain: A Report on
the Family Census of 1946, H. M. S. 0., London,
1954, especially Chapter VII of Part I.
9 U.S. Bureau of the Census, Current Population Reports, Series P-20, No. 108, Washington
(July 12, 1961).
Some Selected Findings of the Princeton Fertility Study: 1963
133
lie women believes that their religion
takes a position in favor of large families.
Although further research is necessary to
isolate the social mechanisms by which a
norm of high fertility is sustained, we
were able to determine that a Catholic
education is one of the social mechanisms
supporting such a norm. It seems to operate primarily at the college level, to some
extent at the secondary school level, and
not at all at the elementary school level.
Although a process occurs to select the
more religious individuals into Catholic
educational institutions, the education
itself seems to exert an effect on fertility
independent of this selectivity. There is
RELIGION
One of the main emphases in this study certainly ground for research into the nahas been on the connections between re- ture of the influence exerted since it unligion and fertility from which the follow- doubtedly functions at both formal and
informal levels.
ing generalizations have emerged:
The ethnic origin of Catholics is also a
Religious preference, that is preference
factor
affecting fertility although it is by
for the Protestant, Catholic, or Jewish
no
means
independent of religiousness.
faith, is the strongest of all major social
Catholics
of
Irish heritage both want and
influences on fertility. Catholic couples
want the most and Jewish couples the have the most children with those of Italifewest children with Protestants in an in- an origin tending to be at the opposite end
of the continuum.
termediate position.
The influence exerted by religion operSOCIO-ECONOMIC STATUS
ates primarily through its effect on the
Studies
of the fertility of socio-economnumber of children desired and only secic
classes
of the population have been
ondarily through fertility-planning sucabundant
in
demography and constitute
cess. To oversimplify somewhat, Catholics
one
of
the
main
foundations of the socioloby and large appear to want larger families and they have them. Their compara- gist's interest in the area of fertility. In
tively ineffective fertility planning should recent years much research in the United
be viewed mainly in terms of child-spac- States has revealed a clear contraction of
ing. The assumption, based on findings class difference in fertility. Part of this
discussed earlier, is that once their larger contraction may be due to different relafamily ambitions are realized their success tionships between socio-economic status
in controlling family size improves. At the and fertility for Protestants and Cathopposite extreme are the Jewish couples olics.
who want the fewest number of children
Regardless of the way in which socioon the average and whose fertility plan- economic status is measured (including
ning is extremely successful.
subjective measures), fertility is negativeContrary to our own expectations, we ly associated with the socio-econoInic stafound that only a small minority of Catho- tus of Protestants and positively related
10 P. K. Whelpton and C. V. Kiser, eds., Social
to the socio-econoInic status of Catholics,
and Psychological Factors Affecting Fertility, Milalthough
in neither case is the relationbank Memorial Fund, New York, 5 vols., 1946ship
strong.
There are several important
58.
SOCIAL AND PSYCHOLOGICAL FACTORS
Investigation into the social and psychological factors affecting fertility follows a line of inquiry begun with the Indianapolis Study.'? Although some of our
earlier interests were directed toward personality and attitudinal levels of explanation, the most successful probes have been
in the more conventional sociological
areas of differential fertility where our
classifications presumably reflect sub-cultural normative systems delineated by religious, educational, occupational, residential and other dimensions.
134 DEMOGRAPHY
implications of this finding which we will
not elaborate here.
Socio-economic status is less strongly
related to fertility than is religion-a generalization that is valid even considering
the opposite directions of association in
the two major religious groups.
Another line of research pursued in this
study was prompted in large part by
Goldberg's re-analysis" of Indianapolis
data as well as data from other more recent studies." His observation is that the
socio-economic differential in fertility
may be largely a reflection of rural-urban
differences in the background of the different socio-economic classes. Our analysis confirms this hypothesis in part:
In the Protestant population, the negative association of fertility with socioeconomic status diminishes and tends to
become positive among couples with several generations of urban living. Among
Catholics, however, the positive relationship is maintained at approximately the
same magnitude for all classes regardless
of rural or urban background.
One of the outstanding findings of
the Indianapolis Study (of Protestant
couples) was that the relationship between socio-economic status and fertility
was negative for the total sample but positive for couples who had planned their
fertility successfully. This finding was important for what it implied about the future relationship between the two variables as contraception becomes more
popular and more effective. Our study
confirmed this finding among Protestants
as well. Among Catholics, however, socioeconomic status and fertility correlate
positively in the total sample as well as
among successful planners.
11 David Goldberg, "Another Look at the Indianapolis Fertility Data," Milbank Memorial
Fund Quarterly, 38 (1960), pp. 23-36. See also
David Goldberg, "The Fertility of Two-Generation Urbanites," Population Studies (March
1959), pp, 214-22.
12Ronald Freedman and Doris P. Slesinger,
"Fertility Differentials for the Indigenous NonFarm Population of the United States," Population Studies, 15 (1961), pp. 161-73.
The relationship between socio-economic status and the extent of planning
fertility successfully also follows an opposite pattern for the two religious groups.
For example, among Protestants the relationship between education and fertility-planning success is positive while
among Catholics it is negative. The explanation for this apparent paradox is the
concentration of Catholics who attended
college in the Catholic higher educational
system. When the association is examined
for Catholics whose education is secular
the same pattern is found as for Protestants. This clearly requires an important
qualification in traditional generalizations
about the relation of education to family
planning.
SOCIAL MOBILITY
Probably no hypothesis received more
attention in this study than that connecting fertility with social mobility, a variable that was measured in numerous different forms. There is very little more
that can be added to a conclusion of essentially no relationship. There are some
indications, as for the socio-economic status dimension itself, that what little association exists follows opposite directions
for Protestants and Catholics.
ECONOMIC RECESSION
Between the first round of interviews
in 1957 and the second round conducted
in 1960 an economic recession as well as
a major steel strike occurred in the
United States. We were the recipients
quite fortuitously of an experimental opportunity to examine the effects of macroeconomic events on the fertility of individuals directly involved. The steel strike
seems to have exerted no effect on fertility, but the recession produced a twofold effect. Two main negative effects
were distinguished: a reduction in income
and unemployment. The former experience was characterized by lower fertility
while the unemployed group actually appeared to have experienced somewhat
Some Selected Findings of the Princeton Fertility Study: 1963 135
higher fertility than the bulk of the
sample unaffected by the recession. The
latter finding was interpreted in terms of
planning capabilities underlying both economic and fertility behavior.
NEXT STEPS
We will skip over other findings, or
rather lack of findings with personality
variables and numerous measures of social
relationships within the family and conclude with a few remarks about the third
and final phase of this study. We are now
starting to interview the sample for the
last time. We are beginning with the oldest couples who have been married the
longest time and who expressed desires for
no more children and continue the interviewing over a five-year period ending
with the youngest women in the sample.
The primary objective of this final interview will be to secure data on completed family size with which we will be
able to evaluate further the validity of the
numerous propositions advanced above.
The third interview will also afford us the
opportunity to extend our inquiry into
the relation of religion and fertility, e.g.
by obtaining data on the respondents'
communal involvement in religion. We
are also asking direct questions on abortion in an attempt to get some estimate of
incidence in a good though specialized
sample. Incidentally, if our pretest experience is any guide there is no difficulty in
asking such questions. And finally, the
longitudinal design of our study will allow
further methodological inquiries into the
reliability of survey data on family planning.