This study analyzed more than 35,000 survey answers collected from 1988 up to 2024 as part of the American National Election Studies, a long-running project tracking US public opinion since 1948.
It looked at key political topics like economics, race, and inequality. Abortion and traditional family values stood out with big shifts-as progressive views increased, it pulled people further apart compared to the late ’80s when conservatives weren’t so consistently against abortion, for example.
Public opinions on health insurance and discrimination against African Americans also moved notably in different directions-showing what the researchers call “true polarisation.”
On issues about equality, the left-right divide has stayed wide for a while now. Still, the team noticed that polarisation has gone up significantly across every single issue they checked.
They also found that “sorting”-meaning how much folks identify strongly with a party or ideology-has jumped quite a bit since the late eighties.
By 2024, there are 20% more people on the left side who say they’re Democrats and 51% more who call themselves liberals than back in ’88. Meanwhile, on the right wing, 30% more claim to be Republicans and 39% describe themselves as conservatives compared to Reagan’s time ending.
“Sorting increases the difference between Democrats and Republicans even when attitudes don’t change much, so it can be hard to gauge what is driving political polarisation,” said De-Wit.
“Using machine learning, we can see that both are happening. People are sorting themselves more using political labels, alongside a genuine increase in polarisation on the core issues.”
Dr David Young added: “In the past, someone with left-wing views on one issue might have held right-wing views on another. That’s rarer now.”
“I think this consolidation happens as people pick up clear cues from political elites about what goes together. It makes average positions more extreme, and widens gaps between US citizens.”
Still though, De-Wit points out that polarization may seem worse than it really is in America. “Political groups have moved further apart in recent years, but these divisions are still fuzzy, and Americans are not split into entirely opposing tribes when it comes to the issues.”
Despite these opinion changes, both sides-the left-leaning and right-leaning groups-have stayed about the same size since ’88. The variety of views inside each group hasn’t gotten bigger either; only the gap between them has grown wider.
The new research also shows that America isn’t like most countries around the world where one side tends to be bigger than the other politically.
In their Royal Society paper, Cambridge researchers share global results by running similar clustering methods on answers from over 173,000 people across 57 countries from ’99 through 2018.
“In developing countries you usually find a big culturally conservative majority with a smaller liberal minority. In highly developed nations we often see socially liberal majorities-but just barely,” said Young.
“The United States is unusual because its left and right groups are almost equal in size. This has been true for quite some time and might explain why polarization here feels so intense.”
Unlike in America though, they didn’t find clear signs that political opinions worldwide are getting more polarized overall. This study was funded by Templeton World Charity Foundation.
