Seth Richards - Shubik “ Peer Effects in Sexual Initiation : Separating Demand and Supply Mechanisms ”

Most work on social interactions studies a single, composite effect of interactions within a group. Yet in the case of sexual initiation, there are two distinct social mechanisms— peer-group norms and partner availability—with separate effects and different potential interventions. Here I develop an equilibrium search and matching model for first sexual partners that specifies distinct roles for these two mechanisms as part of demand and supply. I estimate the model using a national sample of high school students, with data over time on individual virginity status. The results indicate that peer-group norms have a large effect on the timing of sexual initiation for both boys and girls. Changes in opposite-gender search behavior (i.e., partner availability) also have a large impact on initiation rates for boys, but not for girls. The existence of a composite effect of social interactions is also confirmed using a standard method: instrumental variables estimation of linear regressions. ∗I thank my thesis advisors for their dedication, support, and hours of their time: Kenneth I. Wolpin, David M. Cutler, Elena Krasnokutskaya, and Áureo de Paula. I am also grateful to John Cawley, Guy David, Steven N. Durlauf, Sara Markowitz, Ellen R. Meara, and Nirav Mehta for helpful comments, and to the National Bureau of Economic Research for computer facilities. This research uses data from Add Health, a program project designed by J. Richard Udry, Peter S. Bearman, and Kathleen Mullan Harris, and funded by a grant P01-HD31921 from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, with cooperative funding from 17 other agencies. Special acknowledgment is due Ronald R. Rindfuss and Barbara Entwisle for assistance in the original design. Persons interested in obtaining data files from Add Health should contact Add Health, Carolina Population Center, 123 W. Franklin Street, Chapel Hill, NC 27516-2524 ([email protected]). No direct support was received from grant P01-HD31921 for this analysis. †Email: [email protected]