Perceptions and evidence about undocumented immigration to the United States.

The past 20 years have witnessed dramatic changes in the volume and composition of immigration to the US. As the number of immigrants has risen the perceptions both of the public and of policymakers have increasingly focused on the costs rather than the benefits that may be associated with the arrival of newcomers to this country. The wages of undocumented immigrants do not appear to be affected by their immigrant status and studies of labor market impacts have consistently found that the effects of immigrants on the wages and earnings of other labor force groups are either nonexistent or small. However public perceptions have often run in the opposite direction. The following are reasons for development of such a gap between perceptions and research results. 1) Observers have often failed to specify the population to which estimates refer. Undocumented population estimates usually refer to the population stock or the size of the population in the country at a particular time. The flow of persons into and out of the country over a given period may be much larger. The flow of undocumented immigrants may exceed the stock and create the impression that the stock is larger than it really is. 2) It is likely that the Census has enumerated a higher proportion of permanent settlers than temporary settlers and that estimates of the size of the undocumented population are more accurate in the case of permanent settlers. 3) Many legal immigrants speak only limited English; their increasing presence in the country may have fostered the impression that the undocumented population is larger and is growing faster than is actually the case. Moreover legal immigrants have been found to exert a small negative effect on the wages and earnings of other groups thus inviting the generalization that undocumented immigrants might have the same effect. However undocumented Mexican immigrants appear to generate small increases in the earnings of some other groups. 4) The ethnic composition of legal immigrants has changed over the past 20 years to include higher proportions of Hispanics and Asians. Since most undocumenteds are of these national origins the growing presence of legal immigrants may have generated confusion about differences between the size and growth of the legal and undocumented populations. 5) A number of highly respected representatives of the academic community have advanced arguments to the effect that undocumenteds exert a negative impact on the economy. 6) A substantial time lag often exists between the development of policy concerns and the accumulation of research evidence relevant to those concerns.