Federal Reserve Chairman Jerome Powell is shifting monetary tightening into a higher gear. His goal sounds straightforward—lift interest rates to “neutral,” a setting that neither spurs nor slows growth.

But there’s a catch: Even in normal times, no one knows where this theoretical level is. And these aren’t normal times. There are good reasons to think the ground beneath the central bank’s feet is shifting and that, after accounting for elevated inflation, neutral may be higher than officials’ recent estimates.