IntroductionThe paper is a brief investigation into the level and type of among the Mexican-born workers into the U.S. labor market. Mexicans make up the largest immigrant group in the U.S. and they are integral part of the workforce. As of 2014, as BLS reported1, there were 8.8 million (documented) immigrant workers of Hispanic or Latino ethnicity. It is safe to assume that a significant majority of them are Mexican-born. These immigrant workers are making 21 percent less than their native-born Hispanic/Latino counterparts. For the undocumented immigrants, the gap is even larger. For instance, Riverra-Batiz (1999) found that legalization had a significant positive on the earnings of undocumented immigrants. This may be caused by elimination of the monopsonistic power that some employers have over them by allowing immigrants greater access to the labor market.The status and unique characteristics of immigrants, documented or not, have been the subject of many studies. We are particularly interested in their cultural integration/assimilation and the associated economic outcomes.1. Cultural Integration and language acquisitionDifferent immigrant groups display different assimilation characteristics. Mexicanimmigrants generally rank far lower in the Assimilation Index, compared to other countries2. For instance, in 2007, immigrants' assimilation level was measured to be only one-third of the Cuban-born immigrants. They also tend to naturalize very slowly. Of those who arrived between 1975 and 1980, only around 45 per cent had become citizens by 2007. The same rate is around 90 per cent for Vietnamese and around 65 per cent for Italians (Vidgor, 2009).Language skills, along with years spent in the U.S., are generally thought to be a good proxy to measure the level of cultural integration. If English language proficiency is a good proxy for cultural integration, immigrants from Mexico appear to have integrated into American society less rapidly than other groups: only a dismal 49 per cent of immigrants are fluent in English compared to 80 per cent fluency among non-Mexican immigrants. A half of discrepancy, as Lazear (2007) calculates, could be explained by concentration of immigrants in enclaves: those who live in concentrated areas learn English less rapidly and obtain less education. This is what Chiswick (1978) called Mexican ethnic-group effect resulting in initially lower earnings compared to other immigrants. This pattern is only exaggerated by the fact that immigrants on average expect to stay in the U.S. for a shorter time period of time than non-Mexican immigrants.We intend to demonstrate the extent to which cultural measured by English proficiency and age-at-arrival in the U.S. determines the status of immigrants in the job market and, more importantly, whether or not the return on integration varies between El Paso, TX, and Pima, (AZ), two border counties with a heavy immigrant presence. The paper is organized as follows: first, we will study the theoretical and empirical literature that articulates the role of English speaking skills and age at time of migration in determining occupational segregation, and in turn earnings, among Mexican-origin workers. Secondly, we will introduce our data and methodology. Lastly, we will present and interpret the results of our multinomial regression analyses.2. English Skills, migration age and occupational sorting: a literature overviewThere is a modest literature on the effects of language acquisition on labor market outcomes. One of the earlier works in the field was conducted by Rivera-Batiz (1992), using the 1985 Young Adult Literacy Assessment survey, a nationally representative household survey of persons 21 to 25 years old. A reading proficiency test was given to each individual (in place of a self-assessed spoken English rating). …