The sociodemographic characteristics of Mexican immigrant status groups: implications for studying undocumented Mexicans.

"Based on Warren and Passel's...estimate that nearly two-thirds of Mexican-born noncitizens entering the U.S. during 1975-80 and included in the 1980 Census are undocumented immigrants, this article uses the 1980 Public Use Microfiles to delineate four Mexican origin immigrant status groups--post 1975 Mexican-born noncitizens, pre-1975 Mexican-born noncitizens, self-reported naturalized citizens, and native-born Mexican-Americans." It is found that "the pattern of sociodemographic differences among these groups provides support for the idea that the first two categories contain a substantial fraction of undocumented immigrants. These two groups (especially the first) reveal characteristics that one would logically associate with undocumented immigrants--age concentration (in young adult years), high sex ratios, low education and income levels, and lack of English proficiency."