Book excerpt: We use the 1990 and 2000 Mexican and U.S. population censuses to test Borjas's negative-selection hypothesis that the less skilled are those most likely to migrate from countries with high skill premia/earnings inequality to countries with low skill premia/earnings inequality. We find that Mexican immigrants in the United States are more educated than nonmigrants in Mexico; and were Mexican immigrants to be paid according to current skill prices in Mexico, they would be concentrated in the middle of Mexico's wage distribution. These results are inconsistent with the negative-selection hypothesis and instead suggest that there is intermediate selection of immigrants from Mexico.