This paper is a critical review of and a reader's guide to a collection of papers by Robert E. Lucas, Jr. about fruitful ways of using general equilibrium theories to understand measured economic aggregates. These beautifully written and wisely argued papers integrated macroeconomics, microeconomics, finance, and econometrics in ways that restructured big parts of macroeconomic research.

We measure price-level uncertainty and instability in the United States over the period 1850 to 2012. Major outbreaks of price-level uncertainty and instability occur both before and after World War II, alternating with three price-level moderations: one near the turn of the twentieth century, another under Bretton Woods, and a third in the 1990s. There is no evidence that the price level was systematically more stable or less uncertain before or after World War II. Moderations sometimes involved links to gold, but the experience of the 1990s proves that a well-managed fiat regime can achieve the same outcome.