The U.S. must face one of two scenarios: Either the next president will face a recession in office, or the U.S. will have the longest economic expansion in its history.

Odds are that the recession is more likely. Economists in The Wall Street Journal’s latest monthly survey of economists put the odds of the next downturn happening within the next four years at nearly 60%.

That is not an assessment that the next U.S. president will cause a downturn. Rather, it is a recognition that throughout its history the American economy has never grown for more than a decade without a recession. Over the course of the next four years, something—whether exhaustion of the economy’s cyclical momentum, a policy mistake from the Federal Reserve or some outside shock—could knock the economy off course.

“We do not think expansions die of ‘old age’ but there’s more probability that a shock will hit the U.S. economy further out in the horizon,” said Lewis Alexander, chief U.S. economist at investment bank Nomura.

The current expansion began in June 2009, and has now continued for 88 months, making it the fourth-longest period of growth in records stretching to 1854.