The Lowdown on Apportionment

By Claire Low, Targeting & Analytics Director, All On The Line

At All On The Line, we are eagerly awaiting the first release of 2020 Census data and new apportionment calculations, which will determine each state’s total number of congressional districts for the next 10 years and each state’s power in the electoral college. Before the U.S. Census Bureau releases the data next week, we thought we’d share what to expect when it announces the apportionment numbers, including anticipated population trends, congressional seat allocation predictions, and the variables we will be closely monitoring on Apportionment Day.


Let’s start at the beginning. Apportionment is the process by which the Census Bureau assigns the number of congressional districts to each state for the next decade following a census count.

Traditionally, the Census Bureau completes and delivers these calculations to the president by December 31 on years ending with zero. That would have been December 31, 2020. However, the pandemic and actions taken by the Trump administration pushed back the timeline. This year, the Census Bureau announced this data would be available no later than April 30.

Using a mathematical formula called the “Method of Equal Proportions,” the census divides the 435 seats in the U.S. House of Representatives among all 50 states based on total population in each state. Total population is determined by population counts collected from the latest decennial census, which the Census Bureau completed last fall. This formula ensures that each state, no matter how small, receives at least one congressional seat, and minimizes population discrepancies between state’s congressional districts.

Apportionment is calculated from total population counts — not citizen population, registered voters, or even likely voters. This is important because Congresspeople represent everyone who lives in their district, not just citizens or voters. After all, everyone in a given district might use the same roads and bridges or health centers, and everyone deserves to have an advocate to help them sort out social security checks or veteran benefits.

You may have heard media buzz about the Trump administration’s attempt to exclude undocumented persons from the apportionment count in an attempt to weaponize the 2020 Census for partisan gain. But, thanks in part to lawsuits supported by our 501(c)(3) affiliate, the National Redistricting Foundation, apportionment will be derived from total population figures, consistent with historical practice and the bedrock principle of democracy that everyone counts equally.

On Apportionment Day, we should expect to see two important datasets: total population numbers for each state and the number of congressional seats each state will be allocated. And, for the first time, the census will also release documentation on data quality indicators surrounding the census count. These data quality metrics will provide insight on how households were resolved across multiple data collection modes.

It’s important to note that this apportionment data is just the first major data release from the Census Bureau that we’ll see this year. This release will not include data more granular than statewide figures. Instead, map drawers will have to wait until later this year to receive neighborhood-level data, known as the PL 94–171 files, to draw actual maps.


Over the last decade, we have witnessed rapid growth in the Sunbelt, in states such as Texas, Florida, and North Carolina, while population has declined or remained relatively stagnant in the Midwest and Northeast, in states such as Illinois and Pennsylvania. And while many large cities have experienced minimal growth, we have seen a rise in suburban and exurban communities across the country.


There are only 435 voting members of the U.S. House of Representatives despite the growing size of the national population. Because there are a fixed number of seats, this makes reapportionment a zero-sum game. A gain by one state will result in another state or states losing seats in direct proportion to that seat gain. It also means that states that have technically grown since 2010 can lose congressional representation, because the state failed to keep pace with the rest of the country.

Based on the latest population estimates released by the census at the end of last year, we believe nine states will lose at least one seat, while seven states will gain at least one additional seat. We forecast Texas will experience the largest change, as it is on track to gain three seats and may grow its congressional delegation from 36 to 39 members.

A full census count and small shifts in population can determine if a state will actually lose or gain a seat in the final calculation. The latest population estimates suggest that a few states are close to gaining or losing additional seats, and we’ll be monitoring for those tradeoffs on Apportionment Day:

  • New York loses one seat or two. New York could have either 25 or 26 seats for the next decade.
  • Alabama loses a seat. If New York keeps 26 seats, it would likely result in a six-member delegation from Alabama, down from seven members.
  • Minnesota loses a seat. We are also keeping a close eye on Minnesota. We project, and have projected for several years now, that Minnesota loses its eighth seat, but the state is currently on the bubble between 7–8 seats.
  • Texas gains two or three seats. Texas may have 38 or 39 seats for the next decade.

Apportionment Predictions


Once the Census Bureau releases apportionment data, states will know with certainty their congressional representation for the next decade. And, map drawers can also calculate how many people will need to reside in each congressional district. The “one person, one vote” principle requires states to draw equally populated congressional districts, down to the person, and this data release will facilitate those calculations.

Despite all that we will know about the congressional landscape by this time next week, the map-drawing process can’t start just yet. Map drawers will need to wait until the full dataset, which will be available prior to September 30, to draw actual maps. In the meantime, commissions, elected officials, and map drawers can and should start engaging communities, soliciting feedback from constituents, and considering where congressional seats should be added or removed.

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