The first is the simple accumulation of experience that has exposed some of the shortcomings in earlier thinking about macroeconomic policy. The second is the advances in the analytic framework available to policy-makers to help them analyze the workings of the economy and of monetary policy. These are not independent factors, of course, since economic analysis does change in response to experience.
In this case, it was the inability of the previous framework to provide a satisfactory explanation of the developments in the second half of the 1960s and the 1970s that led to changes in the framework for analyzing the macroeconomy. 21  Porter Commission Report, pp. 477-478.