hard to be confident that this was populism's high­water mark without a better understanding of what caused the rise in the first place.The most convincing explanations suggest that populist upswings are not in the past.

　　It is attractive to dismiss the rise of populism as an unavoidable after­effect of the global financial crisis.Studies show that the vote shares of extreme parties，particularly on the right，tend to increase in the years after the crisis.The Depression produced some of the 20th century's most dangerous and strong populist movements.But the facts do not fit that story precisely.In Europe，for example，populist parties have steadily won more voters since the 1980s.What's more，populist anger is rarely focused on finance.Trade and immigration are more prominent targets.The clearest recent phenomenon of the populist rush-Mr Trump's victory and Brexit(英国脱欧)-has only an indirect link to the financial crisis.

　　Rival theories blame populism on deep cultural insecurities caused by demographic(人口的) and social change.In a forthcoming paper Noam Gidron and Peter Hall argue that right­wing political success is built on a decline in the subjective social status of white men.Both economic hardship and relative improvements in the perceived(感知的) status of other groups，such as women and racial minorities，seem to contribute to male insecurity.Around 2010 American women without a college degree overtook similarly educated men when both self­assessed their place in the social ladder.Men's perception of their relative status has also fallen in Europe.The paper links declining status to support for right­wing populism.Yet this also seems only a partial explanation.The recent rise in left­wing populism has been just as striking.

　　A third explanation is proposed by Dani Rodrik of Harvard University，who argues that globalization is like "an elephant in the room".He suggests that populism may become more attractive as global integration(一体化) matures.Cutting taxes on imported and exported goods by that extra little bit causes much smaller increases in GDP than previous reductions and delivers less noticeable consumer benefits；but such cuts continue to put costs on unlucky workers.Eventually this unbalance produces a strong negative reaction.

　　These theories are reasonable.But they are still incomplete.The rejection of established elites(精英) is perhaps the major characteristic of a populist movement，yet what is not always clear is why mainstream parties should be so indifferent in the face of disagreement.In another new paper，Luigi Guiso，Helios Herrera，Massimo Morelli and Tommaso Sonno provide a clever framework for answering that critical question.Establishment parties，they suggest，cannot respond to supporters' concerns because of their respect for institutional restrictions，like the rules of the European Union.

But keeping faith with institutions can mean letting down voters.When elected leaders fail to deliver hoped­for improvements，the public disengages.Depressed turnout(票数) is an opportunity for political adventurers.Almost regularly，the authors argue，populists promise to relieve the