Figure 2 shows the teen birthrate since 1976, using Vital Statistics data.2 The
teen birth rate holds roughly constant through the late 1970s and most of the 1980s
between 50 and 55 births per 1,000 women between the ages of 15 and 19. A large
blip developed in the time series beginning in the late 1980s, and the teen birth rate
rose to a level of around 60 births per 1,000 teenage women in the early 1990s. It has
been generally declining since then. The teen birth rate was 37.9 per thousand in
2009, down from the peak of 61.8 in 1991. Figure 2 also shows that the composition
of teen births has shifted dramatically towards unmarried women. The birth rate
among unmarried teens used to be considerably lower than that for all teens, but
in 2009, 87 percent of teen births were to unmarried mothers (Martin et al. 2011).
Trends in teen births can be driven by changes in the likelihood of a pregnancy
or changes in the likelihood of aborting a pregnancy once it occurs (we assume
miscarriage rates are roughly stable over time). Figure 2 also displays trends in the
pregnancy and abortion rate, again as measured per 1,000 women age 15 to 19.
Pregnancies and abortions were roughly flfl at during the period in which teen births
were flfl at through the late 1980s. During this period, roughly 10 percent of teens got
pregnant and 4 percent had an abortion each year. The spike in teen births in the
early 1990s was driven almost entirely by an increase in the pregnancy rate; almost
12 percent of teens got pregnant at the peak in 1990. Clearly, the recent decline in
teen births is not attributable to greater use of abortion; instead, it is the result of