The way Pew Research Center calculates the estimated number of unauthorized immigrants in the United States is the product of decades of work by Jeffrey Passel, senior demographer, along with former colleagues at the U.S. Census Bureau and the Urban Institute. Passel has written numerous studies on the demography of immigration and on immigration issues.

Read more here for his answers to some common questions about the research techniques used to derive the unauthorized immigrant population estimate.

How Pew Research Center Counts Unauthorized Immigrants in the U.S.