AMERICAN GIRLS BECOME pregnant far more often than girls in other developed countries—twice as often as girls in England or Canada and nine times as often as girls in the Netherlands or Japan. Still, data show that teen birth rates have declined in the United States, and researchers have tried to find out why. The Annie E. Casey Foundation summarized research on the declining birth rate:

There are two primary reasons that teen birth rates are falling: (1) Fewer teens are having sex, and (2) more of the teens that do have sex are using contraception. . . . Researchers attribute the recent trends in teen sexual activity and contraceptive use to a variety of factors: (1) greater emphasis on delaying sexual activity; (2) more responsible attitudes among teenagers about casual sex and out-of-wedlock childbearing; (3) increased fear of sexually transmitted diseases, especially Acquired Immune Deficiency...