How and when political polarisation increased in the US

Political and social divisions in the US have grown by 64 per cent since the late 1980s, with almost all of the growth occurring after 2008. This is the conclusion reached by researchers from the University of Cambridge, having analysed changes in public attitudes over almost four decades.

The work, published in the journal Royal Society Open Science, covers the period from the end of the Reagan era to 2024 and is based on data from the American National Election Study (ANES), including more than 35,000 respondents.

2008 as a turning point

The analysis shows that during the 1990s and early 2000s, the level of polarisation in American society remained relatively stable. However, starting in 2008 - amid the financial crisis, the election of Barack Obama and dramatic changes in the media environment - the divergence between left and right views began to grow steadily.

According to the head of the study, Lee de Wit, 2008 was the key point after which disagreement on most social and political issues began to grow.

Shift to the left as a major factor

The study shows that the increase in polarisation is not mainly due to the radicalisation of right-wing views, but to the liberal part of society moving in a more progressive direction.

According to the data, the American left was on average 31.5 per cent more socially liberal in 2024 than it was in 1988. Meanwhile, right-wing views became only 2.8 per cent more conservative over the same period.

The authors note that this asymmetry may create a sense of "shifting ground" among right-wing voters who see much of society changing faster than they do.

How polarisation was measured

Unlike many previous studies, the Cambridge team's work did not rely solely on respondents' party self-identification. Instead, the scientists used machine learning algorithms that grouped people by their positions on specific issues - from abortion and racial inequality to family values and social policy.

According to lead author David Young, this approach allows for a more objective assessment of real differences of opinion beyond party labels.

On which issues the gap has grown the most

The greatest increase in polarisation was recorded on the issues of:

• abortion,

• traditional family values,

• health insurance,

• discrimination against African-Americans.

On some topics, the divergence was intensified by the movement of both sides, which researchers call "real polarisation". On issues of equality, meanwhile, the gap between left and right has remained consistently high for decades.

Political identities have become more rigid

The study also found a rise in so-called "sorting" - an increasing overlap between political views and party identity.

Since 1988:

• 20 per cent more people in the left-wing group have identified themselves as Democrats and 51 per cent more as liberals;

• in the right-wing group, 30 per cent more people identify themselves as Republicans and 39 per cent as conservatives.

According to the authors, this reinforces the sense of division, even when the views themselves are not changing so dramatically.

Why the split is felt most acutely

At the same time, the researchers emphasise that American society has not divided into completely isolated camps. The size of the left and right groups has remained roughly the same since the late 1980s, and the diversity of views within each group has not increased. It is the distance between them that has changed.

The US, the authors say, stands out from most of the world in that the left and right camps here are historically equal in size. This makes any increase in polarisation particularly noticeable and tense.

A global analysis by the same team found no comparable increase in polarisation in other countries.