evidence: Border Patrol apprehensions of migrants at the U.S.-Mexico border are on the rise again. Although the majority of people attempting to enter the United States illegally are stopped, this trend could foreshadow an increase in the U.S. unauthorized immigrant population after years of relative stability. Yet the activity at the southwestern U.S. border is only one part of the overall story of unauthorized immigration, as a growing share of this population came from regions other than Mexico or Central America and entered the U.S. legally but overstayed their visas. [...] Based on experience and research, we know the census counts and other official surveys tend to miss some people. Unauthorized immigrants are especially likely to be missed. Therefore, we do a further assessment of potential undercounts or undercoverage. Based on this additional research, our final estimate of the U.S. unauthorized immigrant population includes an upward adjustment for undercount. (Our 1990 estimate comes from work by Robert Warren and John Robert Warren; details can be found here.) [...] The U.S. unauthorized immigrant population rose rapidly from 1990 to 2007 before declining sharply for two years and stabilizing at 10.5 million in 2017. Pew Research Center’s most recent estimate is well below a peak of 12.2 million in 2007, but roughly triple the estimated 3.5 million in 1990. The estimate includes 1.5 million or more people who have temporary permission to stay in the U.S. through programs such as Deferred Action for Childhood Arrivals (DACA) and Temporary Protected Status (TPS), as well as people awaiting decisions on their asylum applications; most could be subject to deportation if government policy changed.