In practice, however, the great expansion of higher education has coincided with a productivity slowdown. Whereas in the 1950s and 1960s workers’ output per hour across the rich world rose by 4% a year, in the decade before the covid-19 pandemic 1% a year was the norm. Even with the wave of innovation in artificial intelligence (ai), productivity growth remains weak—less than 1% a year, on a rough estimate—which is bad news for economic growth. A new paper by Ashish Arora, Sharon Belenzon, Larisa C. Cioaca, Lia Sheer and Hansen Zhang, five economists, suggests that universities’ blistering growth and the rich world’s stagnant productivity could be two sides of the same coin.