of stateless persons, but has severe limitations. Federal immigration datasets track “nationality,” but may or may not include a dropdown for statelessness. The “nationality” variable typically lists persons of “unknown” nationality, a designation that includes, but is not exclusive to those who are potentially stateless or potentially at risk of statelessness. In addition, the federal government has restricted the public’s access to relevant federal datasets and to systems manuals that could explain codes, variables, and data entry procedures. Furthermore, immigration- and refugeerelated data would cover only those stateless persons (not all) who come to the attention of federal officials. Nor does this data yield complete or reliable estimates of those known to federal officials. Based on these data limitations, CMS opted to make the US Census Bureau’s American Community Survey (ACS) data the centerpiece of its profiles of populations that are potentially stateless or potentially at risk of statelessness in the United States. Among possible data sources, the ACS provides the most detailed demographic, social and economic data, and it covers the widest number and array of US residents who are potentially stateless or potentially at risk of statelessness. CMS supplemented the ACS with administrative data on refugee and immigrant populations encountered by federal officials. The ACS covers roughly one percent of the US population. Each year, it gathers detailed data – including for non-naturalized foreign-born persons – for all states and for cities, counties, metropolitan statistical areas, and Public Use Microdata Areas (PUMAs), a Census-defined geographic area of 100,000 people or more. CMS queried ACS data on foreign-born non-citizens using characteristics from the profiles of stateless groups from around the world whose members are or may be in the United States. It developed these profiles based on UNHCR reports, government and academic literature, survey responses, and interviews with stateless persons. Based on the ACS data, CMS estimates that there were 198,000 non-US citizens among the 2017 US resident population that fit its profiles of potentially stateless persons or those potentially at risk of statelessness.15 However, some profiles included variables—such as some ethnicities, languages and countries of origin—that are not available through the ACS, thus precluding estimates for these populations based on the ACS. To complement its ACS estimates, CMS secured data from the US Department of State’s (DOS’) Worldwide Refugee Admissions Processing System (WRAPS), a database that tracks the admission of refugees for resettlement. WRAPS does not permit the calculation of estimates for all groups for which CMS compiled ACS-based estimates, but it does permit estimates from some populations for which ACS estimates were zero or could not be calculated. CMS’s analysis of WRAPS data revealed an estimated 117,370 refugees that fit the profiles of potentially stateless persons or those potentially at risk of statelessness, including 20,320 from profiles for which ACS estimates were zero or not possible to produce. Adding CMS’s ACS estimates and its WRAPS estimates—for profiles for which ACS estimates were zero or not possible to produce—yielded an overall estimate of roughly 218,000 US residents who are potentially stateless or potentially at risk of statelessness. Because CMS’s WRAPS estimates cover populations not in the ACS data, its overall estimates do not “double” count those who are potentially stateless or potentially at risk of statelessness. 15 CMS also calculated upper and lower bounds for this estimate. CMS estimates that the number of individuals who are potentially stateless or potentially at risk of statelessness falls between 192,000 and 204,000 persons. 4