Almost three decades ago, one of us, Jack Goldstone, published a simple model to determine a country’s vulnerability to political crisis. The model was based on how population changes shifted state, elite and popular behavior. Goldstone argued that, according to this Demographic-Structural Theory, in the 21st century, America was likely to get a populist, America-first leader who would sow a whirlwind of conflict.

Then ten years ago, the other of us, Peter Turchin, applied Goldstone’s model to U.S. history, using current data. What emerged was alarming: The U.S. was heading toward the highest level of vulnerability to political crisis seen in this country in over a hundred years. Even before Trump was elected, Turchin published his prediction that the U.S. was headed for the “Turbulent Twenties,” forecasting a period of growing instability in the United States and western Europe.