From Davis and Lay-Yee (1999)

     Average Age of first experience,

     first intercourse

              First Sexual     First Intercourse

                Experience

 
Age

Cohort

  45-54           16.3              20.4

  35-44           15.5              18.0

  25-34           15.0              17.7

  18-14           14.6              17.2

Center for Disease Control, U.S (Youth Risk Behavior Survey)

        % sexually active grade 9-12 students

       (had intercourse in preceding 3 months)

1991                  38%

1995                  38%

1999                  36%

2003                  34%