What share of the increase in the U.S. undocumented population since 2021 is due to visa overstays versus border crossings?
Executive summary
The balance of evidence in the reporting shows that visa overstays were the dominant source of new unauthorized residents for many years before 2021, but the post‑2021 surge in the U.S. undocumented population reflects an unusual inflection: large increases in border encounters, humanitarian paroles and pending court cases have driven much of the growth since 2021 even as overstays remain a substantial and continuing source; however, the sources do not provide a single, authoritative percentage split for the share of the increase since 2021 attributable to overstays versus border crossings, so any numeric attribution must be treated as an informed inference rather than a definitive measurement [1] [2] [3].
1. Historical baseline: overstays dominated new annual entries before the surge
Multiple demographic analyses and government summaries establish that in the decade before 2021 visa overstays increasingly outnumbered unauthorized border crossings as the principal annual contributor to the undocumented population: researchers and think tanks documented that overstays accounted for a growing share of newly undocumented arrivals through the 2000s and 2010s, with some studies finding overstays exceeded border entries for several consecutive years and comprising roughly 40% or more of the stock of undocumented residents by the late 2010s [1] [4] [5].
2. What changed after 2021: a surge of border encounters and parole that shifted flows
Since 2021 the dynamics changed: Migration Policy and other analysts identify a sharp rise in irregular arrivals at the U.S.–Mexico border, coupled with broad use of humanitarian parole and administrative releases, which together produced large inflows and a marked expansion in the unauthorized population in 2021–2023—an expansion that would not be explained by overstays alone [2] [3].
3. Overstays remained large but did not solely drive post‑2021 growth
Congressional and DHS‑based measurements place annual visa overstays in the hundreds of thousands—estimates of roughly 650,000–850,000 overstays per year across FY2016–FY2022—so overstays continued to add materially to the undocumented population after 2021, including notable contributions from nationals such as Venezuelans whose visa patterns changed during that period [6]. These continuing large annual overstay figures mean overstays are a persistent component of growth even amid a border surge [6].
4. The reporting’s quantitative gap: no single source gives an exact post‑2021 share
The assembled sources—academic reviews, Migration Policy Institute, CMS, Pew summaries, and CRS/DHS reporting—agree on the qualitative picture (rising border arrivals plus sustained overstays) but do not converge on a single, verifiable percentage breakdown of the net increase in the undocumented population since mid‑2021 that can be cited with precision; Migration Policy shows the population reached its highest level amid record border encounters and parole use [2] [3], while other analyses document the long‑running dominance of overstays in prior years [1] [5], leaving an evidentiary gap for an exact share since 2021.
5. Best synthesis and plausible interpretation
Combining the reporting: longstanding, large annual overstay counts (hundreds of thousands per year) continued after 2021 and therefore account for a meaningful portion of the increase, but the extraordinary spike in border encounters, releases and parole in 2021–2023 represents a major, possibly majority, driver of the observed net rise in the unauthorized population over that interval; the literature supports the claim that before 2021 overstays were the largest single annual contributor, while the post‑2021 expansion is best characterized as a mixed phenomenon dominated in that window by irregular border flows and administrative admissions [1] [6] [2].
6. Caveats, competing interpretations and why precise attribution is hard
Data challenges undercut any attempt at a crisp percentage: the “unauthorized population” depends on stocks plus inflows and outflows (deportations, voluntary departures, deaths, transitions to legal status), DHS/CBP encounters include expulsions and paroles that don’t map neatly to long‑term additions, and researchers use differing definitions and methods (residual estimation, administrative exit data, cohort analyses), so alternative readings exist and the sources themselves caution that exact partitioning of growth into “overstay” versus “border crossing” shares since 2021 is not reliably available from public reporting alone [7] [2] [3].