Revisiting the Relationship between Inflation and Output Gap in Iranian Economy Using Wavelet Transform Approach

The purpose of this paper is to revisit the relationship between inflation and output gap by using wavelet coherence approach. This approach attempts to combine the classical time series analysis with frequency domain analysis, and presents the advantages of assessing the co-movement of two series in the context of both time and frequency dimentions. Using continuous wavelet transform approach, the relationship between inflation and output gap, by considering GDP with oil sector and without oil sector, was studied by annual and quarterly data from 1959 to 2016 in Iran. The results showed that in the long run, the relashionship between inflation and output gap is positive. This result confirms existence of a Phillips curve with negative slope in the long run. However, the relationship between the two variables in the short term and also for the period before Islamic Revolution reflects a Phillips curve with positive slope. Friedman noted this type of curve for high inflation economies for a period of several years in 1977 in his Nobel Prize lecture. This result could have been very important in testing Phillips curve theory in Iranian economy.