With less than three months until the US presidential elections, it feels that the country has never been as polarized as it is at the moment. While polarization trends have been conclusively shown at the party system level, much less is known about the extent to which party polarization is mirrored by affective polarization among voters, i.e. the extent to which citizens feel more negatively toward other political parties than toward the one they identify with. A second shortcoming of the literature is the lack of cross-country research when it comes to the comparison of trends in affective polarization.

A new paper on affective polarization by scholars Levi Boxell (Stanford University), Matthew Gentzkow (Stanford University) and Jesse M. Shapiro (Brown University) now compares trends in affective polarization in nine OECD countries (Australia, Canada, New Zealand, Norway, Sweden, Switzerland, the UK, the US and (West) Germany) over the last forty years. The paper uses a unique data set assembled from survey responses of individuals answering questions about their party allegiance and their opinions on other parties.

Maybe unsurprisingly, the US exhibited the largest increase in affective polarization over the last four decades. In three other countries (Canada, New Zealand, and Switzerland) polarization rose as well, but to a lesser extent. In a plurality of countries, affective polarization fell, namely in Australia, Britain, Norway, Sweden, and (West) Germany. However, if only the years after 2000 are considered, all countries except Germany, Norway, and Switzerland show an increase in affective polarization which makes the trend in the US appear somewhat less distinctive. Nevertheless, the increase in affective polarization is larger in the US than it is anywhere else in the countries studied.

What accounts for this trend? The authors distinguish between developments that are observable in all or most countries in the sample, like an increase in inequality, and factors that are more distinctive in the US. They point to changing party composition, growing racial divisions, and the rise of cable news that “receive more support as potential explanations in our data”. These results are in line with recent survey results that show that about 7 out of 10 democrats would not consider dating a Trump voter. This shows that polarization goes beyond political parties and policies. Instead, party polarization and voter polarization go hand in hand with one feeding off of the other.