Not so long ago, during the age of Milton Friedman, the chief concern of monetary policy was inflation. The Federal Reserve’s job was seen as a balancing act: Too low a money supply would slow spending, and too much would erode purchasing power. Of course, given the inoculation of monetary economists against anything resembling deflation, we really only worried about erring in the other direction. Good monetary policy meant open-market operations to keep the money supply on a predictable path, which gives markets a stable foundation for short-term and long-term contracting, facilitating economic coordination.