The proportion of 15- 19-year-old girls who are sexually active rose from 47% in 1982 to 55% in 1990, and is decreasing again.
The percentage of high school students who have remained virgins has risen from 45.6% in 1990 to 54.1% in 2001.
Fifty-six percent of teenage girls and 73% of teenage boys today have had sexual intercourse by their 18th birthday. In the early 1970s, 35% of girls and 55% of boys had had sex by that age.
Most very young teenage boys and girls have not had intercourse — 84% of 13-year-olds, 77% of 14-year-olds and 70% of 15-year-olds.
While the likelihood of having intercourse increases steadily with age, 1 of every 5 teenagers do not have intercourse during their teenage years.
Seven of 10 girls who had sex before age 14, and 6 of 10 of those who had sex before age 15 report having sex involuntarily.
Most teenagers begin having intercourse in their mid-to-late teens, about 8 years before they marry.
Among the most common reasons teens have sex, according to 55% of teens, is that "they think they're ready."
Six of every ten teenage girls say one reason why teen girls may have sex is because a boyfriend is pressuring them.