Social network effects in contraceptive behavior among adolescents.

OBJECTIVE: To quantify empirically the role of peer social networks in contraceptive behavior among adolescents.

METHOD: Using longitudinal data from a nationally representative sample of adolescents, the authors use a multivariate structural model with school-level fixed effects to account for the problems of contextual effects, correlated effects, and peer selection to reduce the potential impact of biases from the estimates of peer influence. The peer group measures are drawn not only from the nominations of close friends but also from classmates. Contraception use among the peer groups was constructed using the peers' own reports of their contraceptive behavior.

RESULTS: Controlling for parental characteristics and other demographic variables, the authors find that a 10% increase in the proportion of classmates who use contraception increases the likelihood of individual contraception use by approximately 5%. They also find evidence that the influence of close friends diminishes after accounting for unobserved environmental confounders.

CONCLUSION: The findings of this study support the findings in the literature that peer effects are important determinants of contraception use even after controlling for potential biases in the data. Effective policy aimed at increasing contraception use among adolescents should consider these peer effects.