How would excluding unauthorized immigrants from the census have affected congressional apportionment after 2020 and projections for 2030?
Executive summary
apportionment">Excluding unauthorized immigrants from the apportionment base would have produced small but tangible seat changes after 2020—Pew’s analysis finds California, Florida and Texas would each have lost one seat compared with the baseline apportionment that included everyone [1], while multiple academic papers and news outlets conclude the partisan consequences would have been negligible, with no more than two House seats and three Electoral College votes switching between parties over the 1980–2020 period [2] [3] [4]. Projections for 2030 diverge: some analysts (notably CIS) argue continued immigration growth could amplify the redistribution by 2030, while peer-reviewed demographic work emphasizes that the net partisan impact historically has been minimal and that future effects depend heavily on uncertain migration trends [5] [2].
1. What happened in the 2020 apportionment if unauthorized immigrants were excluded?
Independent modeling of the 2020 apportionment shows a clear, concentrated effect: Pew’s projection that removes unauthorized residents from the apportionment count produces one fewer seat each for California, Florida and Texas compared with the official baseline that counted everyone, and corresponding gains for some smaller states [1] [6]. Other mainstream analyses reach similar narrow conclusions: multiple outlets report that omitting people without legal status would not have flipped party control or produced wide partisan swings in 2020, though the exact states affected vary slightly by methodology [4] [7].
2. How big would the partisan consequences have been?
Two demographers’ peer-reviewed work summarized in PNAS/PMC finds that excluding undocumented residents from apportionment from 1980–2020 would have shifted no more than two House seats and three Electoral College votes between parties in any year, a scale insufficient to change control of Congress or determine presidential outcomes in that period [2] [3]. News reporting and fact checks echo this: inclusion of unauthorized immigrants has historically produced only marginal partisan effects and does not translate into a decisive electoral advantage for one party [4] [8].
3. Why do some groups claim larger impacts?
Analyses that aggregate all foreign‑born residents—legal and unauthorized—and project them forward reach much larger estimates: the Center for Immigration Studies (CIS) calculates immigration (legal and illegal plus U.S.-born children of immigrants) could account for dozens of House-seat shifts and warns those effects could grow by 2030 if immigration remains rapid [9] [5]. These studies use different baselines and inclusions (foreign‑born versus strictly unauthorized), and that methodological choice explains much of the divergence from Pew and PNAS results [9] [5].
4. What about official policy fights and legal context?
The debate has not been purely academic: a Trump administration memorandum argued excluding illegal aliens from the 2020 apportionment could change allocations by “two or three” seats and urged their removal from the base [10], prompting litigation and political countermeasures; civil‑rights groups successfully challenged exclusionary moves and the Census Bureau kept counting everyone for apportionment purposes [11]. The Constitution’s text and prior litigation are central to whether and how such exclusions could be implemented, and that legal fight shaped the practical outcome for 2020 [11].
5. Looking toward 2030 — uncertainty and the range of forecasts
Forecasts for 2030 split along assumptions about immigration trends: CIS projects that if recent rapid growth continues, immigration’s redistributive effect on House seats will increase further by 2030 [5], while the academic literature cautions that historical experience shows only small partisan shifts attributable to undocumented residents and that future impacts hinge on migration volumes, geographic settlement patterns and the still‑fluid legal/policy landscape [2] [3]. In short, excluding unauthorized immigrants from 2030 apportionment could matter more if net migration rises sharply and concentrates in fast‑growing states, but current peer‑reviewed work suggests large partisan flips are unlikely absent dramatic demographic change [5] [2].