U.S. teenagers' sexual behaviours became more cautious between 1991 and 2005.(Sex Research Update)

Unlike Canada where population-based surveys of key sexual health behaviours are conducted only sporadically, in the U.S. such behaviours are regularly monitored through the Centers for Disease Control and Prevention's biannual Youth Risk Behavior Surveys (YRBS) which asks a number of specific questions related to sexual behaviour: "Have you ever had sexual intercourse?", "During your life, with how many people have you had sexual intercourse?" "During the past 3 months, with how many people have you had sexual intercourse?" and "The last time you had sexual intercourse, did you or your partner use a condom?" In addition, respondents are asked about birth control pill use and whether they have been taught about HIV/AIDS in school. The YRBS has been conducted biannually since 1991 and is administered through an anonymous, self-administered questionnaire to a nationally representative sample of high-school students in grades 9-12 in all 50 states.

While public and media perceptions of adolescent sexual behaviour often assume that teens are increasingly more likely to be sexually active and at earlier ages, the YRBS continues to indicate otherwise. During the 1991 to 2005 period, the percentage of high school students who reported ever having sexual intercourse declined by 13% from 54.1% in 1991 to 46.8% in 2005. According to Brener, Kann, Lowry et al. (2006), who analyzed the data on behalf of the CDC, "Logistic regression analyses indicated a significant linear decrease overall and among female, male, 9th grade, 10th grade, 11 grade, 12th grade, black and white students" (p. 852). Among Grade 9 students, the percentage who had ever had intercourse dropped from 39.0% in 1991 to 34.3% in 2005. However the percentage of Hispanic students who reported ever having intercourse did not significantly decline over the 1991 to 2005 time period. The percentage of students who reported having had 4 or more sexual partners in their lifetime decreased from 18.7% to ...