Right now, the four most populous democracies in the world are ruled by populists: Narendra Modi in India, Donald Trump in the United States, Joko Widodo in Indonesia, and Bolsonaro in Brazil. That makes it rather important to know which scholars are correct: Either democracy is in the midst of an unprecedented global retreat, or we’re witnessing a salutary course correction in which citizens are finally holding global elites to account for their failures. (Or, if Ferguson is right, nothing much will change.)

Read: What is a populist?

The most obvious way to settle this urgent matter is to look at the impact that populist governments have actually had on democracies in the past. To that end, we constructed a comprehensive database of populist governments. Doing so was an inherently fraught exercise: If you ask three scholars about the nature of populism, you are liable to get five different answers. Besides, populism is not like a light switch that is either on or off; some leaders exhibit certain (but not all) classic characteristics of populism.

Here’s how we formed our list: We selected 66 leading peer-reviewed journals in political science, sociology, and regional studies; identified all articles published in these journals on the subject of populism, as well as political leaders linked with populism; then vetted each potential case study, consulting with country and regional experts. Populist governments, in our working definition, are united by two fundamental claims: (1) Elites and “outsiders” work against the interests of the “true people,” and (2) since populists are the voice of the “true people,” nothing should stand in their way.

Ultimately, we identified 46 populist leaders or political parties that have been in power across 33 democratic countries between 1990 and today, giving us the ability to settle the theoretical debate about the tension between populism and democracy in a rigorous, empirical way, on a global scale, for the first time. The results were alarming: Populists are highly skilled at staying in power and pose an acute danger to democratic institutions.

On average, ordinary democratic governments remain in office for a brief span of time: three years. Six years from their first election, four in five non-populist governments have already been booted from power. Populist governments, by contrast, manage to sustain their hold on power for a significantly longer stretch; on average, they hold on for about six and a half years, or more than twice as long as their non-populist rivals.

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Populists aren’t just more likely to win reelection once or twice; they are also much more likely to remain in power for well over a decade. Six years after they are first elected, populist leaders are twice as likely as non-populist leaders to still be in power; twelve years after they are first elected, they are more than five times as likely.