How "democratic" is Congress?

The US Senate has 100 members, 2 from each of the 50 states, regardless of the population of those states. Non-state territories like Puerto Rico and the District of Columbia have no senators.

If we sort the states from largest to smallest and then graph them with (cumulative) number of senators on the horizontal axis and (cumulative) population on the vertical axis, we see how unevenly the population is distributed among senate "districts" (i.e., states).

The 9 largest states account for 50% of the country's population. Half of the Senate represents about 83% of the population, while the other half represents another 16%. 1% has no representation whatsoever in the Senate.

The House of Representatives is designed to be more equally representative, following the idea of "one person, one vote". If we sort the House's 435 districts by population and graph them in the same way, the result is much closer to a straight diagonal line.

There are still little jumps. There's a big one at the beginning: Puerto Rico is the size of about 4 average-sized districts but has no voting representatives. Around representative #417, there's another little jump because the District of Columbia has more people than almost 20 districts, but also has no voting representatives.

With 435 districts, it's hard to see from that graph that there's real variation in the population of each district. The number of representatives hasn't changed since 1929, and districts can't cross state borders, so some states end up with more or fewer districts - and each district with more or fewer residents - than if each district had the same number of people.

If all districts had the same number of people, they would each have about 770,500 people. But in reality, some districts, like Montana's at-large district, have many more people, which means less voting power per person. Others have many fewer residents than the average district, but they still get one representative in the House.

The data for the House of Representatives comes from the 116th Congress (2019-2021), which were in effect before the redistricting that followed the 2020 census. Once the new district data is available from the American Community Survey, we can recreate these graphs for the districts that will take effect in January 2023.

This analysis was inspired by "American Democracy Was Never Designed to Be Democratic", by Louis Menand in The New Yorker.

Data sources

State population data source: Annual Estimates of the Resident Population for the United States, Regions, States, District of Columbia, and Puerto Rico: April 1, 2020 to July 1, 2021 (NST-EST2021-POP) (Link).

Senators data source: https://www.senate.gov/senators/index.htm

Congressional district population data source (116th Congress): 2021 American Community Survey 1-Year Estimates (DP05) (Link).