"In this paper, we examine net emigration from Mexico over the period 1960 to 2000. The data are consistent with labor-supply shocks having made a substantial contribution to Mexican emigration, accounting for one third of Mexican labor flows to the U.S. over the last 25 years of the 20th century. Net emigration rates by Mexican state birth-year cohort display a strong positive correlation with the initial size of the Mexican cohort, relative to the corresponding U.S. cohort. Labor-demand shocks also contribute to emigration, but the state-specific component of these is muted relative to labor supply. In states with long histories of emigration, the effects of cohort size on emigration are relatively strong, consistent with the existence pre-existing networks. In states without a history of emigration, the effects of cohort size on emigration accelerate as a cohort ages, consistent with the creation of new networks"--National Bureau of Economic Research web site.