We test for a change in the volatility of 214 U.S. macroeconomic time series over the period 1959–1999. We find that approximately 80% of these series have experienced a break in unconditional volatility during this period. Even though more than half of the series experienced a break in conditional mean, most of the reduction in volatility appears to be due to changes in conditional volatility. Our results are robust to controlling for business cycle nonlinearity in both mean and variance. Volatility changes are more appropriately characterized as instantaneous breaks than as gradual changes. Nominal variables such as inflation and interest rates experienced multiple volatility breaks and witnessed temporary increases in volatility during the 1970s. On this evidence, we conclude that the increased stability of economic fluctuations is widespread.

This paper proposes an iterative procedure to discriminate between structural breaks in the coefficients and the disturbance covariance matrix of a system of equations, with recursive procedures then identifying individual coefficient shifts and separating volatility from correlation breaks. Structural breaks in short-term cross-country inflation relations are then examined for major G-7 economies and within the euro area. There is evidence that the euro area leads inflation in North America, while changing short-term interactions apply within the euro area. Covariability generally increases from the late 1990s, while euro-area countries move from essentially idiosyncratic contemporaneous variation to comovement in the 1980s.