"Estimates of the medium- and long-term economic and budget outlook rely on projections of the size and composition of the nation's population. One challenge to such projections is forecasting how many immigrants will come to and stay in the United States. Because most immigrants are of working age when they arrive, rates of net migration are critical in determining the growth of the labor force. Indeed, over the past decade, foreign-born workers accounted for more than half of the growth of the labor force. Moreover, the composition of the immigrant population could also make a difference to the outlook. This paper examines the projection methodologies and outlines the most recent projections of the Social Security trustees and the Census Bureau. The trustees' projections are higher than those of the Census Bureau in the near term but lower after 2025. The paper then addresses issues about those projections raised by the 2003 Technical Panel on Assumptions and Methods. In the panel's view, both the trustees' and the Census Bureau's projections underestimate future net migration. The Social Security trustees and the Census Bureau, along with CBO, are currently evaluating the technical panel's recommendations. Finally, the paper discusses factors that might influence the level and composition of net migration. In principle, one might be able to improve on current projections by explicitly modeling key determinants of both the potential supply of immigrants and the potential demand for immigrant workers. Those theoretical insights may be helpful in assessing broad trends, though at present they appear to be of limited value for quantitative projections."
Congressional Budget Office: http://www.cbo.gov/