The number of years of sexual intercourse an adolescent reports strongly predicts their number of lifetime sexual partners (Shrier, Emans, Woods, & DuRant, 1996). In a study of two nationally representative samples, Santelli, Brener, Lowry, Bhatt & Zabin (1998) show that early sexual debut relates to multiple recent sexual partners and having had six or more lifetime partners. For example, in the study, a young woman who had sex for the first time before age 14 is more than twice as likely to have had multiple recent sexual partners compared with a young woman who had sex for the first time at age 16 or later (Santelli et al., 1998).