Age of first intercourse fell steadily through the 1990s

Evidence

The age of first intercourse has dropped steadily since 1987. In 1995, the female mean was 15.8 years, and that for the males was 16.2. Most (69%) of the unmarried women in my class in January 1995 were not virgins, and most of the nonvirgins had begun having sex before their sixteenth birthday. Ditto for the males, but they had started a little later on the average. — Bob Altemeyer, The Authoritarian Specter, 2263