If you experience any technical difficulties with this video or would like to make an accessibility-related request, please send a message to [email protected]. Roughly 25 million people in sub-Saharan Africa are infected with HIV, and the number is growing. Since 9095 percent of HIV infections in Africa result from heterosexual sex,understanding changes in heterosexual behavior in response to rising HIV rates is crucial to developing effective prevention strategies. In the new study 'HIV and Sexual Behavior Change: Why Not Africa?' Emily Oster, Becker Fellow for the Gary S. Becker Center on Chicago Price Theory at the University of Chicago Graduate School of Business and Assistant Professor of Economics, analyzes the apparent lack of behavioral response among Africans. Most prior estimates of behavioral response have focused on very limited and specialized populations.