Age & sexual activity. Average age of first intercourse, by gender, in the United States (Read more »): Males: yrs Females: yrs Teen sexual activity, contraceptive use, teen pregnancy, abortion, and STIs: American Teens' Sexual and Reproductive Health 28% of Americans over age 45 report they had sexual intercourse once a week or more in the last six months, and 40% report having An Archive of Our Own, a project of the Organization for Transformative Works