Republicans in Congress got a “seats bonus” this election (again)

While Republicans, as of this writing, received a plurality of votes cast for Congress nationwide this year—49.9 percent according data from the Cook Political Report—they received a greater share, 55.2 percent, of the seats. Democrats, as a result, won a smaller share of seats than they did votes: 44.8 percent of seats as compared to 47.3 percent of the votes. (These numbers may change as final vote tallies are updated.)

In the past four congressional elections, then, Republicans, as the party with the majority in the House, received a “seats bonus,” wherein members of their party secured a larger share of the seats in the chamber than the share of votes won nationwide. As we see in the figure below—again using data from Vital Stats and the Cook Political Report—this is a durable feature of U.S. congressional elections. Using the overall vote share (rather than the two-party vote), the figure depicts the difference between the share of the votes and seats won by the party winning the congressional majority. The black line indicates the historical average, at 5.6 percentage points.