Researchers depend on observed regularities in macroeconomic data to guide the development of theory. One problem in developing monetary models of the business cycle is that there seems to be a great deal of instability in nominal data. Using data from 1959:Q1 to 1998:Q4, authors Gavin and Kydland document changes in the cyclical behavior of nominal data series that appear after 1979:Q3 when the Federal Reserve implemented a policy to end the acceleration of inflation. Such changes in cyclical behavior were not apparent in real variables. The authors conclude that in order to find regularities in nominal data sets, it may be necessary to examine and compare episodes with similar monetary policy regimes.