Researchers have shown that the likelihood of sexual intercourse increases with age (Raine et al., 1999; Miller, Norton, et al., 1997 (females only); Brewster et al., 1998; Santelli, Lowry, Brener, & Robin 2000; Jaccard, Dittus, & Litardo, 1999). Further, a younger age at first sexual intercourse is associated with many negative sexual consequences among male and female teens, including a greater likelihood of having nonvoluntary or unwanted sex (Moore et al., 1998), having multiple sexual partners (Smith, 1997) and a greater risk of having a teen birth (Manlove, Terry, Gitelson, Papillo, & Russell, 2000; Smith, 1997; Thornberry, Smith & Howard, 1997).