Percentage of all House votes on which the parties did not split — where a majority of Democrats and a majority of Republicans landed on the same side, 1969–2025. In 1970, 73% of votes were bipartisan. In 2025, 15% were — the lowest ever recorded.
Sources: Brookings Institution, Vital Statistics on Congress, Ch. 8, Tables 8-3 & 8-4 (1969–2022); CQ Roll Call Annual Vote Studies (2023–2025). Plotted as 100 minus the party-unity-vote share: a party-unity vote is one where a majority of Democrats opposed a majority of Republicans, so the remainder is every vote where the two majorities agreed. No House party-unity-votes figure is available for 2023 (shown as a break in the annual line, bridged by the moving average). Full data and methodology: sources.md | Raw data: data.csv