"The The Clinton Foundation notes that child marriage "limits the full potential of girls" and "undermines health, education, economic opportunity, and security." Early wedlock is most common among the world's poorest children. One study found that teen marriage in the U.S. increased by nearly 50 percent in the 1990s thanks to "the spread of abstinence-only-until-marriage sex education at American schools, a shift toward cultural conservatism among some teens and a growing fear among youngsters of contracting AIDS through promiscuity," as the Chicago Tribune wrote in 2004."