Economic activity has remained subdued following the Great Recession. One interpretation of the listless recovery is that recessions inflict permanent damage on an economy’s productive capacity. For example, extended periods of high unemployment can lead to skill losses among workers, reducing human capital and lowering future output. This notion that temporary recessions have long-lasting consequences is often termed hysteresis. Another explanation for sluggish growth is the influential secular stagnation hypothesis, which attributes slow growth to long-term changes in the economy’s underlying structure. While these explanations are observationally similar, they have very different policy implications. In particular, if structural factors are responsible for slow growth, then there might be little monetary policy can do to reverse this trend. If instead hysteresis is to blame, then monetary policy may be able to reverse slowdowns in potential output, or even prevent them from occurring in the first place.