 The Pew Research Center estimated in 2016 that there were 11.1 million illegal immigrants in the US in 2014.These estimates are based on modeling using data from the American Community Survey (ACS) or the Current Population Survey conducted by the United States Census Bureau each year.A 2018 paper by three Yale School of Management professors yielded similar trajectories of the illegal immigrant population, with peak growth in the 1990s and early 2000s followed by a plateau from approximately 2008 onward.