Motivated by long-standing
debates between abstinence proponents and sceptics, we examine how
socio-economic factors influence premarital first births via: (i) age at first
sexual intercourse and (ii) the risk of a premarital first birth following the
onset of sexual activity. Factors associated with an earlier age at first
intercourse will imply more premarital first births owing to increased exposure
to risk, but many of these same factors will also be associated with higher risks
of a premarital first birth following onset. Our analyses confirm previous
findings that women from disadvantaged backgrounds are younger at first
intercourse and have higher premarital first-birth risks than women from more
advantaged backgrounds. However, differences in onset timing have a strikingly
smaller influence on premarital first-birth probabilities than do differences
in post-onset risks. Our findings thus suggest that premarital first births
result primarily from differences in post-onset risk behaviours as opposed to
differences in onset timing...
Our empirical results confirm previous findings that women
from disadvantaged backgrounds initiate sexual activity earlier and have more
premarital first births than those from more advantaged backgrounds. Our hazard
regressions reveal strikingly different effects of covariate for the
transitions to sexual activity and to a premarital first birth following onset.
A standard set of sociodemographic variables have large and statistically
significant associations with premarital first birth risks following onset.
These same variables have smaller associations with onset risk, and only a
subset are statistically significant. These findings provide empirical hints
that some aspects of these two processes may be behaviorally distinct. Results
from decompositions comparing median onset timing for disadvantaged and
advantaged groups show that, net of controls, differences in exposure to risk
have only a small influence on the probability of a premarital first birth, but
that group differences in post-onset risks have a sizeable influence on the
probability of a premarital first birth. This pattern—small effects of
differential exposure to risk but sizeable differences in post-onset
risks—holds for all the variables we examine.
Why might this be? Some insight can be gleaned by
contrasting what is characteristic of sexual onset vs. a premarital first
birth. A higher risk of an event usually implies more individuals experiencing
the event, and our results show that this holds for premarital first births.
Thus, we find that sizeable and statistically significant group differences in
post-onset premarital first birth risks imply equally sizeable group
differences in the probability of such births. Sexual onset is different.
Premarital sexual activity was both close to universal and highly compressed in
this birth cohort of women, with estimated group differences in median ages at
onset of 0.7 to 9.0 months after conditioning on background controls. Taken
together, near universality and compression mean that even sizeable and
statistically significant group differences in onset risks imply only modest group differences in
onset timing.
These results also speak, in part, to policies such as
the abstinence provisions in the 1996 Personal Responsibility and Work
Opportunity Reconciliation Act by providing answers to “what if” questions such
as “What might be the expected consequence for premarital first births were a
policy to delay onset by an amount equal to that for women from intact vs.
nonintact families?” Our results suggest that for premarital first births,
onset timing plays a quite minor role relative to post-onset risks. This
negative finding—that onset timing plays only a minor role—is, we believe,
likely to be robust against factors not observed in our data in that the class
of unobservables needed to reverse this finding will be far smaller than usual.
Our results thus suggest that policies seeking to
influence post-onset behaviors may be far more effective than those seeking to
delay sexual onset. But our findings do not distinguish between a variety of
post-onset factors, including the frequency of post-onset sexual activity;
contraceptive use, knowledge, and consistency; whether pregnancies are planned
or unplanned; abortion availability and utilization; and how such options are
weighed when individuals confront different sets of circumstances. Our results
thus speak to the question of when policies
to reduce premarital first births might be most effective, but say little about which post-onset
behaviors might be most effectively targeted.
Further caution is warranted in that the outcomes we
analyze have been evolving rapidly. In the United States, there have been sharp
declines in teen fertility and steady increases in nonmarital fertility, but
only modest increases in women’s age at first sexual intercourse, with
premarital sexual activity remaining nearly universal. These trends reinforce
our belief that our central finding—that for the probability of a premarital first
birth, onset timing plays a quite minor role relative to post-onset risks—will
likely hold for more recent birth cohorts of women. What has undoubtedly
changed are factors influencing post-onset risks—post-onset contraception has
improved among sexually active teens and young adults, and there have been
sharp increases in births to cohabiting couples. This study thus provides only
a first step towards examining these and other proximate determinants, but our
findings also suggest that future research on such factors may hold substantial
promise for better understanding the behavioral subprocesses underlying
nonmarital fertility...
By: Lawrence L. Wu, Steven P. Martin,
