Controversy over the use of monetary aggregates undermined the impact of the monetarist counter-revolution of the 1970s and early 1980s. Top central bankers accepted Milton Friedman’s dictum “money matters” was valid in some sense, but they were unsure exactly how and why it mattered. Practical application was elusive when their research departments produced data on half-a-dozen monetary aggregates. Which concept of money was of greatest importance – or at any rate of some relevance – to the