The two studies, done by the Centers for Disease Control and Prevention's National Center for Health Statistics, are based on ongoing in-person surveys of Americans done by the government.
The teen survey included about 1,100 boys and 1,100 girls aged 15 to 19. The percentage of girls aged 15 to 17 who said they had ever had sex fell from 38 percent in 1995 to 30 percent in 2002, the center said.
The survey found that 55 percent of all male teens said they had ever had sex in 1995, and this declined to 46 percent in 2002.