At present, the apportionment of House seats to each state and the drawing of district lines are based on total population — not citizenship.1 The nation's 22 million non-citizens, slightly less than half of whom are here illegally, are not evenly distributed across congressional districts.2 As a result, there are many districts in which a large share of the population is not made up of U.S. citizens. It typically requires many more votes to win in districts comprised largely of citizens than in districts with large non-citizen populations. This raises important questions about the principle of "one person one vote" because the inclusion of non-citizens in apportionment and redistricting means that the number of citizens and voters varies enormously by district. This situation also has a partisan dimension, as the presence of non-citizens strongly correlates with support for Democratic candidates.
The findings show:
- The profound impact of non-citizens can be seen in the 12 districts with the lowest share of citizens, which have roughly the same population of voting-age U.S. citizens as the nine districts with the highest citizen shares. This means Americans in the high-citizen districts have only nine representatives in Congress while those in the lowest-citizenship districts have 12, even though the combined populations of citizens are roughly equal.3
- The number of citizens and vote totals in a district can differ partly because of the way House seats are apportioned between the states.4 But even within the same state, where district populations should be even, there were significant distortions caused by immigration in 2018.5
- Texas: The 33rd district, where one-third of adults are not citizens, has 262,000 fewer voting-age citizens than the 21st district, where 6 percent are not citizens.
- Florida: The 25th district, where more than one-fourth of adults are not citizens, has 199,000 fewer voting-age citizens than the 11th district, where 3 percent are not citizens.
- California: The 40th district, where one-third of adults are not citizens, has 233,000 fewer voting-age citizens than the 4th district, where 4 percent are not citizens.
- New York: The 14th district, where nearly one-third of adults are not citizens, has 172,000 fewer voting-age citizens than the 27th district, where 1 percent are not citizens.
- District populations also vary in the number of citizens as they grow at different rates after redistricting occurs every 10 years. But the data from soon after the 2010 census still shows very large differences within the same states.6
- Texas: The 33rd district, where more than one-third of adults were not citizens, had 236,000 fewer voting-age citizens than the 21st district, where 6 percent were not citizens.
- Florida: The 25th district, where more than one-fourth of adults were not citizens, had 176,000 fewer voting-age citizens than the 11th district, where 3 percent were not citizens.
- California: The 40th district, where 38 percent of adults were not citizens, had 246,000 fewer voting-age citizens than the 1st district, where 3 percent were not citizens.
- New York: The 15th district, where more than one-fourth of adults were not citizens, had 190,000 fewer voting-age citizens than the 27th district, where 1 percent were not citizens.
- The citizen share of the voting-age population also has a large impact on turnout. In the five districts with the largest non-citizen shares, roughly half as many votes were cast in the 2018 election than in the five districts with the highest citizen shares. In effect, each voter in the five highest-citizenship districts had about half the influence on the election as voters in the five lowest-citizenship districts.7
- In the 13 House districts where more than one in four adults is not an American citizen, only 158,000 votes were cast on average in the 2018 mid-terms. In contrast, in the 46 districts in which less than 2 percent of adults are not a citizen, 263,000 votes were cast on average.8
- It took many more votes to win a district comprised largely of citizens than it did in districts with large non-citizen populations in 2018. On average, the winning candidate received about 50 percent more votes in the 46 districts where less than 2 percent of adults are non-citizens than in the 13 districts where more than one in four adults is a non-citizen.9
- Districts with large non-citizen shares of the population tend to vote overwhelmingly Democratic, while high-citizenship districts lean strongly Republican, but not as strongly as non-citizen heavy districts vote Democratic.
- Of 16 districts where more than one in four adults is not an American citizen, only one is represented by a Republican. Of the 29 districts where at least one in five adults is not an American citizen, still only one is represented by a Republican.
- In the 46 districts in which less than 2 percent of adults are not American citizens, 41 are represented by a Republican. In the 108 districts in which less than 3 percent of adults are not American citizens, 87 are represented by a Republican.
Data Sources. The Excel spreadsheet included with this analysis provides information on voting, population, and citizenship by congressional district. The citizenship data in this analysis is based on the 2018 American Community Survey (ACS); the 2018 data is the latest data available at the time of this publication.10 The Census Bureau releases ACS data on its website, including socio-demographic statistics by congressional district. The vote totals, including partisan breakdowns for 2018, come from the Office of the Clerk of the U.S. House of Representatives. The clerk's office published "Statistics of the Congressional Election November 6, 2018" on February 28, 2019. Other websites and publications also publish vote totals from federal elections, but the clerk office's statistics can be seen as the official totals. For this reason, we use them in this report.
End Notes
1 Section 2 of the 14th Amendment to the U.S. Constitution states that "Representatives shall be apportioned among the several States according to their respective numbers, counting the whole number of persons in each State." This has generally been interpreted to mean all individuals, not just citizens, are included when seats are apportioned. It is always possible the Supreme Court would approve a reinterpretation of this provision, but this is unlikely, especially in light of other wording in the Constitution. Of course, the Constitution could be amended to exclude non-citizens from apportionment. In terms of drawing district lines within states, the Supreme Court ruled in Evenwel v. Abbott (2016) that states may draw House district lines by total population, but it did not indicate if this is required. So at present it remains undetermined whether a state could draw district lines based on eligible voters, though to do so it would need citizenship data for all persons. At present, the decennial census does not ask all respondents their citizenship. As will be discussed later in this report, the citizenship data in this analysis is based on the American Community Survey, which is a very large survey conducted by the Census Bureau. The survey asks about citizenship, allowing for good estimates of population characteristics, including citizenship, by congressional district. But because it is a survey and not a census, it does not survey all persons. So even if a state wished to draw lines based on the population of citizens, it seems likely that even a survey as large as the ACS would be inadequate to do so. It would instead require the addition of a citizenship question to the census.
2 The 2018 American Community Survey showed 22.1 million individuals who are not U.S. citizens in the United States — 6.8 percent of the total population. Of non-citizens, 20.2 million were adults, accounting for 8 percent of the adult population. The Migration Policy Institute (10.7 million) and Pew Research Center (10.5 million) both base their estimates of the illegal population in part on the American Community Survey (ACS). Both organizations estimate that roughly 5 percent of illegal immigrants are missed in the survey. This means that of the of 22 million non-citizens in the ACS, about 10 million, or 45 percent, are illegal immigrants.
3 The population of the 12 districts with the largest share of non-citizens was 4.84 million and for the combined nine districts with the highest percentage of voting-age citizens the combined population in 2018 was 4.72 million, a 2.5 percent difference.
4 In the apportionment process each state receives one seat regardless of population. Since 1940, the remaining 385 seats are then apportioned to the states using a system called "equal proportions", which determines how the remaining seats are distributed. Some states have populations just below the threshold needed to receive an additional seat while others have a population just enough to get an additional seat and this can produce districts of somewhat different size. Further, seven states have only one representative due to their population; in some cases this makes for a district that is smaller than the national average. However, Montana and Delaware's single districts are the largest in the country because the population of these states is too small to receive a second representative, but is significantly larger than the typical district in a state with many districts.
5 In Wesberry v. Sanders, (1964), the U.S. Supreme Court ruled that districts in the House of Representatives must be roughly equal in population. Earlier and subsequent court cases have reinforced this principle.
6 The 2012 American Community Survey was the first ACS to report statistics that reflected the new districts created after the 2010 census.
7 In the five districts with the largest non-citizen shares, 656,000 total votes were cast in 2018. In contrast, in the five districts with the highest citizen share, 1.22 million votes were cast. In two of the highest non-citizenship districts there was no Republican running, though the Democrat did have opposition from other candidates. In these two districts, the Democrat received about three-fourths of the vote, very similar to the Democratic share in the other three districts where there was a Republican opponent. In short, the presence of a Republican candidate did not seem to make much difference in turnout in the districts with the largest non-citizen populations. In the five districts with the highest citizen shares, both major parties ran candidates in 2018.
8 The 2018 vote totals in the 13 districts with the highest percentage of non-citizens include three where there was no major party opposition, though there was third-party opposition in all three districts. If we exclude these three districts, the average number of votes in the remaining 10 districts was 163,000, which is very similar to the average when these districts are included. The presence of major-party opposition does not make a difference in turnout. The figure for the 46 districts with the highest citizen percentage includes two districts where there was no major-party opposition and the unusually large district that covers the entire state of Montana. Excluding these three districts, the average number of votes in the 43 remaining districts was 260,000, again similar to the average when these three districts are included.
9 The winning candidate in the 13 highest non-citizen districts received 109,000 votes on average in 2018 compared to 163,000 votes in the 46 districts with the highest citizen shares. The 2018 vote totals in the 13 districts with the highest percentage of non-citizens include three where there was no major party opposition, though there were third-party or independent candidates. If we exclude these three districts, the winning candidate averaged 111,000 votes in 2018. In the 46 districts with the highest share of voting-age citizens there were two in 2018 where there was no major party opposition. It also includes the unusually large district that covers the entire state of Montana. Excluding these three districts, the winners in the remaining 43 districts received 160,000 votes on average in 2018. The difference in the vote for the winning candidates when those districts without major party opposition are excluded, along with Montana, is still 44 percent.
10 For comparison, we also provide data from 2012 ACS.