Some Data Issues

Most of our analysis is based on the Current Population Surveys (CPS) of March 1994 and 1995. The relative merits of several data sets for this purpose—the Current Population Survey, the Survey of Income and Program Participation, the Public Use Micro Sample—are discussed in Appendix 7.C. The number of respondents in the combined CPS sample is roughly 300,000, of which about 29,000 are foreign-born. The 1994 and 1995 March CPS were simply pooled, treating each as a separate sample. Because of the way respondents are rotated from one panel to the next, approximately one-half of the data represent reinterviews of the "same" household a year later.

In principle, these surveys cover illegal immigrants as well as legal immigrants and nonimmigrants (foreign students and foreign business travelers). To the extent that these are included in the CPS, they distort the information about immigrants, particularly those who don't stay very long. The problem may not be trivial, since the number of nonimmigrants in the United States at any time is comparable to the annual inflow of immigrants. At shorter durations in the United States, our calculations could most accurately be said to apply to the foreign-born, rather than to immigrants per se. In practice, we do not know the coverage of illegal immigrants, but we suspect that it is incomplete. In our analysis we cannot distinguish between legal and illegal immigrants. Presumably, illegal immigrants both pay less in taxes and receive less in benefits than other immigrants do.6

The Heterogeneity of Immigrants and Intra- and Intergenerational Mobility

The fiscal impacts of immigrants vary greatly depending on a number of their characteristics. The benefits received by immigrants in the United States


average taxes and receive average benefits for people of the ages in the family, and these amounts may be out of line with their exact circumstances. However, since both age and education level of self or parent could be taken into account, this does not seem to be a serious problem for constituting families. For example, low-education families would be more likely to receive Aid to Families with Dependent Children, and this would be reflected in the average numbers.


Readers should also note that the calculations in this chapter are based on estimated relationships between immigrant status, tax payments, benefit receipts, and the like. That is, we use data to calculate these relationships in the CPS sample, and then make inferences about immigrants and natives in general. Inevitably this introduces some margin of error, as a randomly chosen sample is very unlikely to have exactly the characteristics of the entire U.S. population, and there is some measurement error involved in collecting information through any survey. We have no reason to believe that these are misleading estimates, but estimating these relationships adds additional uncertainty about how close our projections of the effects of an additional immigrant would be to the actual effects.

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