There is a steady drumbeat from some corners of Wall Street and some academic economists that the Federal Reserve’s very low interest rates and unconventional monetary policy, inevitably, will create bubbles and financial instability somewhere. Keeping interest rates on Treasurys and bank deposits so low, the logic goes, is inducing investors and financial institutions to “reach for yield,” which is another way of saying that the quest for higher returns is leading them to take excessive risks.

Gabriel Chodorow-Reich, a young Harvard University economist, says, basically, not to worry.