The time-varying Phillips correlation

We use complex demodulation techniques to investigate changes in the correlation between real activity and inflation at the business-cycle frequencies in the United States, the United Kingdom, the Eurozone, and 10 other Organization for Economic Cooperation and Development (OECD) countries over the post-WWII era. Consistent with the analysis of Ball, Mankiw, and Romer (1988) we document a positive correlation between the time-varying average gain of real activity onto inflation at the business-cycle frequencies and inflation's Hodrick-Prescott trend, which is compatible with New Keynesian theories emphasizing the link between trend inflation, the frequency of price adjustments. and the slope of the Phillips trade-off.