"Unlike in the past, recent empirical evidence on migrant selection to the US appears to be at odds with predictions from the basic Roy model. In particular, migrants to the US from many sending countries appear to be positively selected in their education and other observable skills, regardless of the differentials in returns to skill between destination and source (Jasso, et al., 2004; Feliciano, 2005; Kennedy, et al., 2006; Grogger and Hanson, 2011). The case of Mexican immigrants has been analyzed most closely. A high level of income inequality in Mexico suggests that the migrant flow out of Mexico should be negatively selected. Instead, early work found that migrants were drawn from the middle of the educational distribution (Chiquiar and Hanson, 2005; Orrenius and Zavodny, 2005). More recent work based on Mexican panel data finds some evidence of negative selection from Mexico, in the sense that migrants earned less than non-migrants in the period before their trip (see Fernandez-Huertas Moraga, 2011; Ambrosini and Peri, 2012; Kaestner and Malamud, 2013). Differences in the two sets of studies could be due to under-enumeration of undocumented Mexican immigrants in the US Census (Ibarraran and Lubotsky, 2007) or to differential selection patterns by observed skill (education) versus labor market productivity (wages)."