What Is the Size and Legal Composition of the US Foreign-Born Population?

We assess government estimates of the size and legal composition of the US foreign-born population from 2007 to 2015. We examine annual Census Bureau estimates of the total number of foreign born (by citizenship) and annual Office of Immigration Statistics (OIS) estimates of the counts of the three noncitizen categories — legal permanent residents, legal temporary residents, and the unauthorized. Comparison of the annual Census estimates of the number of noncitizens with the estimates implied by the OIS estimates reveals that the OIS estimates are larger than the Census estimates by 3.4–4.7 million over the period. Besides documenting these discrepancies, we describe the data and methods used to produce the estimates, identify the possible sources of discrepancies, propose and implement an approach for reconciling the estimates, and contrast the reconciled estimates with the original estimates. Finally, we provide a foundation for improving estimates of the size of the four major categories of the foreign born, for example, by suggesting new methods to measure citizenship and to estimate such groups as legal permanent residents who become unauthorized. Because in most countries the four foreign-born subpopulations are constrained by distinctive rules, they each have different impacts on their host countries. Estimates of their size are critical for assessments of immigration policy, as differing constraints on employment and entitlement eligibility across these categories means that having accurate counts of their numbers is essential for assessing their economic and fiscal impacts in any country that hosts immigrants.