Monetarism is a school of thought in monetary economics that emphasizes the role of governments in controlling the amount of money in circulation. Monetarist theory asserts that variations in the money supply have major influences on national output in the short run and on price levels over longer periods. Monetarists assert that the objectives of monetary policy are best met by targeting the growth rate of the money supply rather than by engaging in discretionary monetary policy.
Monetarism today is mainly associated with the work of Milton Friedman, who was among the generation of economists to accept Keynesian economics and then criticise Keynes's theory of fighting economic downturns using fiscal policy (government spending). Friedman and Anna Schwartz wrote an influential book, A Monetary History of the United States, 1867–1960, and argued "inflation is always and everywhere a monetary phenomenon".
Though he opposed the existence of the Federal Reserve, Friedman advocated, given its existence, a central bank policy aimed at keeping the growth of the money supply at a rate commensurate with the growth in productivity and demand for goods.