Overview
- Polarization was broadly flat through the 1990s and early 2000s before rising steadily from 2008 to 2024, with signs of a plateau during President Biden’s term.
- The left became 31.5% more socially liberal since 1988, while the right shifted only 2.8% more conservative based on issue positions.
- Authors analyzed more than 35,000 American National Election Studies responses from 1988–2024 using k‑means clustering to group people by issue profiles.
- Issue-based identities and party labels aligned more tightly by 2024, with higher shares in left and right clusters adopting Democrat/Republican and liberal/conservative self-descriptions.
- The United States shows left and right clusters of roughly equal size, with some of the largest changes on abortion and traditional family values, according to the Royal Society Open Science paper.