We examine the behavior of money, inflation, and output under fiat and commodity standards to better understand how changes in monetary policy affect economic activity. Using long‐term historical data for 15 countries, we find that, under fiat standards, the growth rates of various monetary aggregates are more highly correlated with inflation and with each other than under commodity standards. Money growth, inflation, and output growth are also higher. In contrast, we do not find that money growth is more highly correlated with output growth under one standard than under the other.