Vox recently published a story about the “scary” secular stagnation theory, tying it back to a presentation given by Alvin Hansen titled “Economic Progress and Declining Population Growth,” from the American Economic Review in March of 1939.

What is secular stagnation, they ask?

For starters, it has nothing to do with secular versus religious. Instead, the term comes to us from a 1939 presentation given by Alvin Hansen titled “Economic Progress and Declining Population Growth.” In these tailing days of the Great Depression, Hansen was trying to draw a contrast between a cyclical period of slow growth and a structural transformation of the economy. Hansen believed that the world was not experiencing a down period during an up-and-down series of fluctuations. Instead, he said, “we are passing, so to speak, over a divide which separates the great era of growth and expansion of the nineteenth century” from a new era of much slower growth.

Matthew Yglesias goes on: “The Depression, in other words, was not a passing phenomenon but rather something that might last indefinitely.”

A scary theory, indeed.