How have origin-country mixes of the unauthorized immigrant population changed since 2015, and which states saw the biggest shifts?
Executive summary
Since 2015 the unauthorized immigrant population in the United States has grown more diverse: the long-dominant share from Mexico has fallen sharply while arrivals and resident stocks from Central and South America, the Caribbean, and other regions have risen, and the unauthorized population has dispersed geographically beyond a handful of gateway states [1] [2] [3]. State-level patterns are uneven—California’s unauthorized population contracted while other states saw sizable growth or compositional change, producing the largest shifts in states that historically hosted dense Mexican-origin populations and in those receiving new arrivals from Central and South America [4] [3] [5].
1. National picture: Mexico’s shrinking share and rising diversity
Mexico remains the largest single country of origin for unauthorized immigrants but its share of that population has declined markedly since 2015—MPI and allied analyses show Mexico’s unauthorized total fell from a mid‑2000s peak and by 2023 represented a much smaller fraction of the unauthorized population than in 2010, even as the overall unauthorized total grew after 2019 [1] [2]. Concurrently, arrivals and stocks from Central America (notably the Northern Triangle of Guatemala, Honduras and El Salvador), South America (including Venezuela and Colombia), and parts of the Caribbean increased, changing the origin mix and producing a less Mexico‑centric unauthorized population [6] [1] [2].
2. Region- and country-level shifts driving the mix
Analysts document that irregular migration from the Northern Triangle rose after 2015 as insecurity and economic pressures mounted there, making Guatemala, Honduras and El Salvador relatively more prominent sources of unauthorized migrants compared with the earlier Mexico-dominated era [6]. Simultaneously, political crises and economic collapse in parts of South America and the Caribbean—Venezuela, Cuba, Nicaragua and parts of the Caribbean—contributed to growth in those origin groups within the unauthorized population [1] [2]. Migration Policy Institute and Pew work both emphasize that since 2019 the unauthorized population expanded and diversified, with substantial increases in Central and South American origin groups [2] [3].
3. Which states saw the biggest compositional shifts
The geographic footprint of the unauthorized population has become less concentrated: the top six states accounted for 56% of the unauthorized population in 2023, down from 80% in 1990, reflecting both dispersion and changing origin mixes [3]. California—long the epicenter of Mexico‑origin unauthorized residency—was a notable outlier: it experienced a net decrease in unauthorized residents (reported as roughly −120,000 in one series), making it the only large state cited as having declined in a recent Pew summary, and signaling one of the biggest state-level compositional shifts away from a Mexico‑heavy profile [4] [3]. Nevada, California, New Jersey and Texas rank highly in share terms (Nevada with the highest share of households containing an unauthorized immigrant), indicating states where origin mixes matter for local demographics and policy debates [4]. MPI and DHS state profiles and tabulations show that many states that previously had smaller unauthorized populations gained residents from a wider array of origin countries after 2015, but the reporting emphasizes dispersion rather than naming a single group of “fastest changing” states across all data products [7] [8] [9].
4. Drivers of the state-level changes—and the data limits
Multiple forces explain the shifts: changing enforcement and asylum/policy regimes, repatriations and voluntary returns, regional violence and economic collapse in origin countries, and expanded lawful temporary pathways that alter who migrates irregularly [5] [1]. Methodological caveats matter: authoritative estimates rely on residual methods and adjustments to survey undercount; different research teams and DHS produce somewhat different state and country tallies, and some state-level detail is limited by sampling error and modeling assumptions [10] [6] [7]. Where sources disagree, the consistent theme is diversification of origins and dispersion of residence—Mexico’s dominance fell while Central and South American, and Caribbean origins rose—producing the largest compositional shifts in traditional Mexican‑destination states (notably California) and in states absorbing newer origin groups [1] [3] [2].