According to a 1991 study of sexual behavior based on a random sample
of heterosexual under-graduates at a Midwestern university, 80% of the
males and 73% of the females had experienced vaginal or anal intercou
rse. The average age at first vaginal intercourse was 17.2 years for b
oth sexes. Seventeen percent of the sexually experienced males and 18%
of the sexually experienced females had engaged in heterosexual anal
intercourse; among these respondents, the average age at first anal in
tercourse was 20.3 for males and 19.1 for females. Although less than
four years, on average, had elapsed since the respondents had first ha
d vaginal intercourse, males reported an average of 8.0 lifetime vagin
al-sex partners and females reported an average of 6.1. Overall, the f
indings from this random sample of students are similar to those from
a 1988 convenience sample of the same college population.