The fi nal category here is pregnancies not carried to term, which can include
either an abortion or a miscarriage. Abortions are notoriously underreported in
survey data, so by including all pregnancies that are not resolved by birth, we do
not have to worry about separately identifying abortions and miscarriages. Under
the assumption that the rate of miscarriages has been roughly constant over time,
we can interpret trends in so-called uncompleted pregnancies as being driven by
changes in the use of abortion. We see an increase in the rate of uncompleted
pregnancies from 20–25 percent in 1976 and 1977 to about 30–35 percent in the
mid 1980s, followed by a decline back to about 20–25 percent by the mid 1990s and
relative stability in this outcome since then.
Geographic Comparisons of Pregnancies and Abortions
How does the variation in teen birth rates across countries and U.S. states reflfl ect
differences in pregnancy rates and abortion rates?4 We present some summary data
in Table 2. For our international comparison, we highlight numbers from the United
States, United Kingdom, Germany, and Denmark. This set is chosen because abortion
data is available for all four of these countries, and because the countries span
most of the range of country teen birth rates reported in Figure 1. We also report
numbers from Mississippi and New Hampshire, the U.S. states with the highest and
lowest teen birth rates.
The main fifi nding that emerges from these data is that pregnancy rates across
locations line up very closely with birth rates. Differences in pregnancy rates appear
to be the primary driver of differences in birth rates. Nonetheless, there are some
interesting patterns in abortion rates. For instance, the lower rate of abortion in
Germany relative to Denmark means that in Germany more births result from fewer
pregnancies. The United States also has a relatively low rate of abortion conditional
on pregnancy, as compared to the other three countries. This pattern holds despite
the fact that abortion laws are relatively more lenient in the United States, certainly
relative to Germany and the United Kingdom (Levine 2004). We also see that
the lowest teen birth rate U.S. states, like New Hampshire, have teen pregnancy
and abortion rates that are comparable to many other developed countries. In
Mississippi, in contrast, 8 percent of female teens become pregnant each year, and
few have abortions.