Using recent data from southern California and Mexico, we challenge the notion that the demographic profile of Mexican migrants to the United States since 1970 has remained constant. We find that more recent cohorts of migrants are more likely to settle permanently in the United States, to have higher proportions of females, to be younger, to have more education, to be increasingly likely to originate in southern Mexico and the Mexico City metropolitan area, and to be increasingly likely to depart from urban areas within Mexico. Although we find no direct evidence that the legalization programs mandated by the Immigration Reform and Control Act of 1986 has led to a stronger propensity to settle permanently in the United States, logistic regression analyses demonstrate the importance of the other three main explanatory factors suggested by Wayne Cornelius in 1992: economic crisis in Mexico, the changing character of U.S. demand for labor, and social networks.