The teen birthrate declined steadily throughout much of the 1990s. In 1999, the last year for which records are available, the birthrate among teens aged fifteen to nineteen dropped to a record low of 49.6 births per 1,000. The 1999 teen birthrate is the lowest it has been since the National Center for Health Statistics began keeping records in 1940. The rate, which declined every year during the 1990s, fell 3 percent in 1999 and has fallen 20 percent since 1991. The 20-percent decrease has effectively erased the 24-percent increase in teen births from 1986 (50.2 per 1,000) to 1991, when teen births were 62.1 per 1,000.

Many sex researchers and commentators hail the declining teen birthrate as an indication of teens' changing values and beliefs about premarital sex. They believe "abstinence-only" sex education programs— classes in which students are taught only about the benefits of abstinence with no mention of birth control or "safe sex"—are having an effect on...