evidence: While in certain corners of the internet, it is emphatically stated that the U.S. unauthorized immigrant population has swelled by tens of millions over the past few years given the pace of encounters at the U.S.-Mexico border, a new MPI commentary explains why every encounter does not equal an increase of one person in the unauthorized population. [...] The estimates reflect the growing diversification of the U.S. unauthorized population, due both to the decline in the size of the Mexican unauthorized population that began right before the 2008-2009 Great Recession and the widening array of nationalities arriving at the U.S.-Mexico border over the past several years from within and beyond this hemisphere. [...] Source: MPI estimates of the U.S. unauthorized immigrant population, developed in collaboration with Jennifer Van Hook from The Pennsylvania State University, Population Research Institute, are achieved by subtracting the number of legal immigrants from the total of all immigrants for each country and region represented in U.S. Census Bureau American Community Survey (ACS) data. The number of legal immigrants is estimated by adding up all legal admissions from each country and region in every year—using U.S. Department of Homeland Security (DHS) administrative data—and then reducing this number to account for deaths and emigration of legal immigrants. Finally, the unauthorized immigrant population estimates are adjusted upward slightly to account for the recognized undercount of this population in the ACS. For more detail on this methodology, see MPI, "MPI Methodology for Assigning Legal Status to Noncitizen Respondents in U.S. Census Bureau Survey Data."