Keep Factually independent
Whether you agree or disagree with our analysis, these conversations matter for democracy. We don't take money from political groups - even a $5 donation helps us keep it that way.
Fact check: What percentage of US prisoners are illegal immigrants according to 2024 data?
Executive Summary
Official data do not support a single, precise national percentage of U.S. prisoners who are unauthorized (illegal) immigrants for 2024; federal reporting covers only portions of the system, and state and local jurisdictions—which hold roughly 90% of incarcerated people—do not systematically collect citizenship data, making national estimates unreliable [1]. Federal datasets show significant representation of noncitizens in federal prisons and among those sentenced federally, but those figures reflect the federal system only and are not directly transferable to the whole U.S. incarcerated population [2] [3].
1. Why the Numbers Don’t Add Up: A Reporting Gap That Matters
Federal and academic sources converge on a central methodological problem: no comprehensive, nationwide citizenship tally exists for state prisons and local jails, which house about 90 percent of people behind bars; therefore federal counts cannot be extrapolated to the national total with confidence [1]. The Government Accountability Office reported this gap in September 2024, noting federal agencies provide data on noncitizens within the Federal Bureau of Prisons and on federally sentenced populations for specific years, but do not capture citizenship across the broader correctional system [1]. This reporting lacuna means headline claims about the share of “illegal immigrants” among all U.S. prisoners lack a stable empirical foundation.
2. What Federal Data Actually Shows: Noncitizens Are Concentrated in the Federal System
Federal statistics document a clear presence of noncitizens in the federal prison population: the Federal Prisoner Statistics report counted 22,817 non-U.S. citizens in federal prison at yearend 2023, and the Sentencing Commission found that non-U.S. citizens constituted 33.7% of federal sentencings in FY2023, with 88.4% of those identified as illegal aliens [3] [2]. The GAO also documented a downward trend in federal noncitizen counts from 2017 to 2022, a roughly 33 percent decline, and fewer noncitizens sentenced for federal crimes in 2023 versus 2018 [4]. These figures are precise for the federal system but cannot be generalized to state and local facilities without further data [1].
3. What Researchers and Advocacy Groups Say: Lower Crime and Incarceration Rates for Immigrants
Multiple research and policy analyses argue that immigrants—particularly unauthorized immigrants—do not drive higher incarceration rates than native-born Americans. A Migration Policy Institute synthesis and a Brennan Center review found that immigrants are arrested and incarcerated at lower rates than U.S.-born residents, with one analysis reporting undocumented immigrants were 33 percent less likely to be incarcerated than U.S.-born people [5] [6]. These studies do not estimate a national percentage of incarcerated unauthorized immigrants but challenge narratives that equate immigration status with higher criminality, emphasizing population-level comparisons rather than counts within correctional systems.
4. Enforcement Data Shows Criminal-Alien Arrests but Not the Whole Picture
Border and enforcement statistics provide another angle: Customs and Border Protection’s FY2024 Criminal Alien statistics recorded 17,048 arrests of criminal aliens, indicating enforcement activity against individuals with removable or criminally adjudicated status [7]. That figure documents enforcement contact rather than the share of incarcerated people who are unauthorized immigrants nationwide. CBP and enforcement datasets are focused on apprehension and removal proceedings, and they do not translate into a baseline prevalence rate within state prisons and local jails, where the overwhelming majority of incarcerated people are held [1] [7].
5. Interpretive Risks: Extrapolating Federal Data to the Nation Creates Error
Several analyses implicitly warn against extrapolation: federal noncitizen declines and federal sentencing shares are sometimes cited in public debate to imply a national proportion of incarcerated unauthorized immigrants, but such inferences ignore the 90 percent of inmates held at state and local levels with largely missing citizenship data [1] [4]. The GAO’s central finding—lack of comprehensive citizenship data outside federal custody—means that any national percentage asserted without new, representative collection will be methodologically unfounded and potentially misleading [1].
6. Bottom Line for 2024: What Can Be Stated and What Cannot
What can be stated with confidence is that federal prison and federal sentencing data show a sizable noncitizen and illegal-alien presence within the federal system—33.7% of those sentenced federally in FY2023 were non-U.S. citizens, most of whom were illegal aliens, and 22,817 non-U.S. citizens were in federal custody at yearend 2023 [2] [3]. What cannot be stated with authoritative precision is a single percentage of all U.S. prisoners who are illegal immigrants in 2024, because states and localities do not provide unified citizenship counts and federal data are not representative of the total incarcerated population [1].
7. What Would Fix This: Better Data, Better Debate
The GAO recommendation and the broader literature imply a clear remedy: systematic, standardized collection of citizenship data across state and local correctional systems would enable accurate national estimates and more informed policy debate [1]. Until such data exist, analysts and policymakers should avoid presenting federal or enforcement figures as national percentages and should instead contextualize federal counts, highlight downward trends in federal noncitizen populations, and note research showing immigrants generally have lower incarceration rates than the native-born population [4] [5] [6].