In 2016 how many undocumented or illegals were in the USA?
Executive summary
The most widely cited, survey-based estimates place the number of undocumented (unauthorized) immigrants in the United States in 2016 at roughly 10.7–11.4 million, a figure reported by Pew, the Center for Migration Studies, and echoed in DHS analyses [1] [2] [3]. However, alternative demographic-modeling work from Yale/MIT produced much higher figures—reporting a conservative model estimate of 16.7 million and an alternative simulation average as high as 22.1 million—illustrating substantial methodological disagreement [4] [5].
1. Official and survey‑based estimates point to about 10.7–11.4 million in 2016
Multiple established groups using residual and survey methods converged on a total near 11 million for 2016: Pew Research Center’s estimate was 10.7 million [1], the Center for Migration Studies reported roughly 10.8 million [2] and broader compilations and policy briefs commonly cite figures in the 11.0–11.4 million range [3] [6]. These estimates typically start with U.S. Census or American Community Survey counts of the foreign‑born, then subtract legally present immigrants and adjust for undercounts—a technique known as the residual method that underpins many government and research tallies [1] [7].
2. Demographic re‑construction models produce much larger totals—16.7 to 22.1 million
A 2018 academic paper that reconstructed undocumented population flows from 1990–2016 using demographic accounting and parameter simulation produced a “conservative” 2016 estimate of 16.7 million and, under different parameter settings, an average estimate as high as 22.1 million—results the authors and university press coverage framed as a challenge to the conventional 11‑million benchmark [4] [5]. Fact‑checking and reporting outlets noted these higher numbers while contrasting them with the survey‑based consensus, underscoring that the modeling approach can yield far larger totals depending on assumptions about inflows, outflows and undercount rates [2] [5].
3. The disagreement stems from methodology, data gaps, and assumptions—especially about undercounts and overstays
Residual/survey approaches rely on census and household survey data adjusted for known legal immigrants and estimated undercounts; they estimate undercount rates and therefore tend toward lower totals when undercount adjustments are modest [1] [7]. Demographic re‑construction instead sums presumed cumulative inflows and subtracts modeled outflows over decades, making the result highly sensitive to initial conditions and to assumptions about border crossings, visa overstays and emigration—factors that the Yale/MIT paper and its critics explicitly debated [4] [5]. Separate work also highlights that visa overstays made up a growing share of the newly unauthorized in recent years—CMS estimated that overstays accounted for about 62% of the undocumented in 2016—an element that affects trend interpretation even if absolute totals differ [8].
4. Bottom line: a defensible range, not a single settled number
For practical purposes, reporting and policy discussions in 2016 most often used a figure of about 10.7–11.4 million unauthorized residents based on residual and survey methods [1] [2] [6], but an alternative demographic modeling approach argues the population could be substantially larger—conservatively 16.7 million and possibly over 20 million depending on assumptions [4] [5]. The difference is methodological, not merely semantic: acknowledging both strands of research accurately captures the evidence and the uncertainty in the underlying data [7] [2].