It is widely known that about three-fourths of the working-age population is insured for Disability Insurance (DI), but the substantial role played by the Supplemental Security Income (SSI) program in providing disability benefit coverage is not well understood. Using data from the 1996 panel of the Survey of Income and Program Participation (SIPP) we find that over one-third (36 percent) of the working-age population is covered by SSI in the event of a severe disability. Three important implications follow: (1) SSI increases the overall coverage of the working-age population; (2) SSI enhances the bundle of cash benefits available to disabled individuals; and (3) interactions with other public programs—most notably the SSI path to Medicaid coverage—also enhance the safety net. Ignoring these implications could lead to inaccurate inferences in analytic studies.

As the first in a trio of articles devoted to incorporating immigration into policy models, this article traces the history of research on immigrant earnings. It focuses on how earnings trajectories of immigrants differ from those of U.S. natives, vary across immigrant groups, and have changed over time. The highlighted findings underscore key lessons for modeling immigrant earnings and pave the way for representing the earnings trajectories of immigrants in policy models.

Given immigration's recent resurgence as an important demographic fact in the U.S. economy, U.S. policy modelers are just beginning to grapple with how best to integrate immigrants into policy models. Building on the research reviewed in the first article of this series, this article puts forth a conceptual basis for incorporating immigration into a key type of policy model—microsimulation—with a focus on the projection of immigrant earnings.

Complementing the second paper's focus on forecasting immigrant earnings and emigration in a "closed system" for a given population, the last article of the trilogy explores how to project immigrant earnings for an "open system"—a system that includes future immigrants. A simple method to project future immigrants and their earnings is presented.