The past two decades have seen the debate over immigration policy revived by changes in three main indicators. First, the number of immigrants entering the US increased from (roughly) 3.3 million in the whole of the 1960’s to 1 million per year in the 1990’s. Second, those that arrived after 1970 came with considerably lower skills relative to comparable US natives than did previous cohorts of immigrants. Finally, the wage differential between recently arriving immigrants and US natives widened considerably from - 16.6% in 1970 to - 27.6% in 1980, and finally to -31.7% in 1990 (Borjas 1994). These trends show that the performance of immigrants in the US labor market is increasingly relevant not only to immigration policy relating to the rationing of visas, and laws pertaining to illegal immigration, but also to the labor market performance of natives. Chiswick (1978) notes that changes in the skills of immigrants may alter the effects of immigration on the level of income of the native population and on the distribution of this income among groups defined by skill. The growing number of immigrants in recent decades can be interpreted as larger immigrant shares of the US work force. The widening immigrant/native skills differential suggests that the growing immigrant portion is largely under-skilled relative to the US standard.