As journalists and policymakers grow more sceptical of social networks, they frequently discuss social media’s role in political polarisation – including the role of Twitter, a platform widely used by politicians, journalists, and activists in many countries.

There’s some evidence that Twitter helps drive polarisation (such as indirectly shaping the news discourse). However, the data here is contradictory and most research is being done in the US context. In any case, Twitter is a useful source of data that can shed some light on political polarisation. Aleksandra Urman, a researcher from the University of Bern, looked at political polarisation on Twitter from a comparative perspective, using data from 16 countries. The Fix identified the key points from the article.

How to measure political polarisation on Twitter? Check whether the same people are following different political parties.

Urman analysed data from 16 democratic countries, including 11 European nations. To measure polarisation, she downloaded the lists of followers of the official accounts belonging to the countries’ parliamentary parties. She then used an audience duplication approach, analysing overlaps between followers of different parties’ accounts. In other words, the analysis shows how different parties from a certain country share their audience on Twitter.

This method is not a perfect way to measure political polarisation, and it has some limitations. For instance, there’s a likely self-selection bias, stemming from the fact that people who follow political parties on Twitter are more politically engaged than the general population. However, it’s a good way to grasp general levels of polarisation on social media.

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Different levels of polarisation: from “perfectly integrated” Denmark to “perfectly polarised” America

On one end of the spectrum we see Denmark, which has a “perfectly integrated” “political Twittersphere” – meaning that all major parties share Twitter audiences with each other. The United States, South Korea, and Jamaica are all the way on the other side, exhibiting “perfectly polarised” Twitter-based political ecosystems.

Other countries are somewhere in between:

Source: “Context matters: political polarization on Twitter from a comparative perspective” by Alexandra Urman

Electoral systems might explain the differences

It’s hard to be sure about the sources of these differences in (Twitter-based) polarisation levels, but one hypothesis seems likely – electoral systems play a big role. As a general rule, “Polarisation is the highest in two-party systems with plurality electoral rules and the lowest in multiparty systems with proportional voting”.

For example, the “perfectly polarised” United States has a two-party system, with other parties having very little political power and it also has a plurality voting system. By contrast, “integrated” Sweden has a multi-party system with proportional representation.

European analysts shouldn’t rely too much on US data

Most polarisation research out there is US-centered – perhaps because a lot of research overalls is conducted in the US, and America has seen growing political polarisation in recent decades. Urman cautions against generalising based on the US example – its two-party system is an outlier among many other nations.

According to the author, “findings on polarization and social media from the United States have limited generalizability, which is of utmost relevance since most research on the subject is in fact conducted in the US context.”

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What Twitter shows about political polarisation on social media