M ATTEO SALVINI , the head of the Northern League, a populist party that forms part of Italy’s governing coalition, has a pithy explanation for the global rise of movements like his. “It is a common factor,” he says. “The confrontation of the people versus the elite.” Scholars would agree. Since 1999 the University of North Carolina at Chapel Hill has surveyed political scientists about European parties’ policy positions and rhetoric, yielding ideological ratings for each party on various issues. Sure enough, the attribute most correlated with gaining votes since 2014 has been criticism of elites. (The ratings in the survey, conducted roughly every four years, closely match those that voters give to parties when polled, as well as ideological scores that can be derived from manifestos.)

What has drawn voters to such parties? To identify what else they might share, The Economist has used a statistical clustering method to calculate the ideological distances between 244 European parties. Our analysis is based on Chapel Hill’s scores on four issues: social liberalism, economic policy, immigration and the EU .

A familiar left-to-right spectrum emerged for the first three subjects. Parties with free-market economic views also tended to endorse tighter limits on immigration and on personal freedoms. The reverse was broadly true on the left.

Mr Salvini’s League landed on the right, as did most parties with high scores for anti-elite rhetoric. However, some of the fastest-growing upstarts—such as Syriza in Greece, Podemos in Spain and the Five Star Movement in Italy—sat in the middle or on the left. Because of this ideological diversity, no statistically significant relationship exists between the change in a party’s vote share from 2014-18 and its views on immigration, social liberalism or economic intervention by the state.