Is there a direct relationship between inflation and the amount of money printed by the Federal Reserve?

The “Monetarist Approach” considers inflation “always and everywhere a monetary phenomenon.” However, this theory has not played out in the United States and other advanced economies. For example, the U.S. dollar supply grew by 28% between January 2020 and April 2021, but inflation was far lower. In fact, the relationship between the rate of growth of the money supply (minus the rate of growth of GDP) and inflation has been quite unstable for more than 50 years.

Other factors that influence inflation include long-term expectations of inflation among the public and increases in the prices of inputs to the production process, like lumber and oil. Economists also traditionally expect inflation to increase when the economy is producing more than it normally would, but the relationship between the output gap and inflation has been an unreliable predictor of inflation over the past few decades.