Much polarization research comes from the United States, which risks mistaking American peculiarities for universal laws. Looking at other democracies helps separate causes that are shared from causes that are local, and it shows that rising polarization is not inevitable.
Different trends
In a cross-country study, Levi Boxell, Matthew Gentzkow and Jesse Shapiro compared affective polarization over roughly four decades in twelve wealthy democracies. They found that it rose fastest in the United States, rose more modestly in a few others, and fell in several, including Germany. This matters for the media debate in Level 4: the internet and social media spread across all of these countries, yet trends went in different directions. Factors that differ between countries, such as party systems, racial and religious divisions, partisan cable news and elite behavior, look like better candidates for explaining the American rise.
Other research, by Noam Gidron, James Adams and Will Horne, found that measured by level rather than trend, the United States was only moderately polarized compared with other Western publics; in some European countries, such as Spain and Greece, dislike of opposing parties ran higher. The United States stands out more for how fast hostility has grown than for how high it is.
Two parties or many
Party systems matter. In a two-party system, every election is a contest between "us" and "them." In proportional representation systems with many parties, parties often must form coalitions after elections, so today's opponent may be tomorrow's partner. That gives politicians reasons to avoid poisoning relations. Multiparty systems are not immune, though: hostility often concentrates on one or two parties, typically those at the far ends or those seen as outsiders, and new two-camp divides can form.
New divides
Britain's 2016 referendum on leaving the European Union created identities that cut across party. Research by Sara Hobolt, Thomas Leeper and James Tilley found that "Leaver" and "Remainer" identities became, for a time, stronger than many people's party loyalties, with affective hostility to match. This shows that polarizing identities can form quickly around a single high-stakes issue, not only through decades of sorting.
Pernicious polarization
The political scientists Jennifer McCoy and Murat Somer studied countries where polarization helped wear down democracy, including Venezuela, Turkey and Hungary. They use the term pernicious polarization for the point at which a society divides into two mutually distrustful camps along a single dimension, so that every issue becomes a test of loyalty and opponents are seen as threats to the nation.
A recurring pattern in their cases is that a leader exploits or deepens existing grievances, casting the other camp as illegitimate enemies of the people. Opponents, alarmed, sometimes respond with tactics that also strain democratic rules, and the cycle escalates. Their comparative work suggests that once pernicious polarization sets in, it is very hard to reverse, and few countries have managed it.
What reduced it elsewhere
There are historical cases where deep divides were managed. After a bloody civil war and decades of conflict, Colombia's two main parties in 1958 agreed to share power in the National Front, alternating the presidency for sixteen years. It ended mass partisan killing but also shut out other political forces, which contributed to later problems. Postwar Germany built institutions that encouraged coalition and consensus. Such examples show that rules and elite bargains can lower the temperature, though often with costs.
Caution with comparisons
Surveys use different questions in different countries, and parties mean different things in different places. Cross-national numbers should be read as broad patterns, not exact rankings.
Measuring hostility in multiparty systems also takes extra care. A voter in the Netherlands or Sweden may like two or three parties and strongly dislike one. Researchers such as Markus Wagner therefore measure the spread of a voter's likes and dislikes across all parties, weighted by party size, rather than a simple "my side versus your side" gap. Different methods can rank countries differently, which is one more reason to treat any single league table with caution.
Worked example: two elections
Imagine Country A, with two large parties and winner-take-all districts, and Country B, with six parties and proportional representation. In both, an election is close and bitter.
In Country A, the losing party will be out of power entirely for several years. Its leaders have every reason to portray the winners as dangerous, and the winners every reason to govern without them. In Country B, no party wins a majority. The two largest parties, which attacked each other during the campaign, find they must negotiate with each other or with smaller parties to form a government. Within weeks, leaders who called each other reckless are drafting a common program.
Nothing guarantees that Country B's voters feel warmer toward opponents, and multiparty countries can polarize too. But the structure gives its politicians repeated reasons to keep relations workable. That is one reason reformers in two-party countries study multiparty systems, a subject Level 8 returns to.