For women, the median age for first sexual intercourse in 1960 was 19 and the median age at first marriage was 20.3, an interval of only a little over a year. By 1990, the median age at first sex was 16.9 for women, while the age at first marriage for women was 24.5, a gap of 7.6 years. Teenage sex is of concern for various practical reasons. However, maturity and sexual responsibility do not automatically kick in when teenagers turn 20. By most measures, young adults are still involved in a lot of high-risk sexual activity and irresponsible behavior.
Marriage remains the great regulator of sexual behavior.
This decline is largely the result of the rising percent married as age increases. If it is accepted that earlier marriage is not a practical or desirable alternative, then a substantial period of premarital sexual activity is inevitable. There is some evidence that progress may be made in this area.