In fact, median age at first intercourse among women has increased in many countries, particularly in Asia and Latin America (see Table 2). Continued education and delayed marriage may account for some of the increases in Latin America (450). Even where first intercourse tends to occur at a later age than in the past, however, it increasingly occurs before marriage; even where age at first intercourse is rising, age at marriage is rising faster (101, 166).

Premarital sexual activity. As attention focuses on sexual activity among young adults, it often goes unnoticed that in the developing world the majority of young adults, especially young women, are not sexually active and that most sexual activity of young people takes place within marriage (450) (see Figure 1).

Still, in many parts of the world premarital sexual activity is common among young people (see Tables 3 and 4). Its prevalence varies by gender and socioeconomic class. In all societies larger percentages of boys report being sexually active than do girls of the same age, and boys begin sexual activity earlier. For example, in Young Adult Reproductive Health Surveys in Latin America, average age at first intercourse ranged from 13 to 16 years for boys and from 16 to 18 years for girls (337) (see Table 4). In Africa among Kenyan students surveyed in the late 1980s, 48% of males in primary school and 69% of males in secondary school were sexually active, compared with 17% and 27% of girls in primary and secondary schools (255). In Asia, where fewer studies have been conducted, data for Hong Kong, South Korea, and Thailand show that fewer than 10% of unmarried women under age 24 have experienced intercourse (490). In Thailand, however, more than half of boys report having sex by age 18, often with a prostitute (555).

Young men more often report having multiple sexual partners and having intercourse with casual acquaintances. In contrast, young women usually report that they had their first and subsequent sexual relations with a steady boyfriend or fiance (49, 185, 255, 337, 553). Surveys may not always report young people's behavior accurately, however. Young men may exaggerate, reflecting cultural norms that encourage and approve of sexual experimentation for boys, while young women may underreport their sexual activity because of cultural norms that value virginity for girls. As one young woman noted in a Zimbabwe study, "by writing it down, it's like I have to face my own life" (45).

Sexual activity among unmarried youth is increasing in many regions. Over the last 15 years studies in Africa and Latin America have reported increasing percentages of unmarried young adults who are sexually active (15, 156, 283, 336, 337, 349, 350). At least one researcher points out, however, that casual sexual activity is also more common now among adults, both married and unmarried, as well as among youth (292).