Do global output gaps help forecast domestic inflation? Evidence from Phillips curves for Poland

This study confronts domestic and global views on inflation through the use of the Hybrid New Keynesian Phillips Curve (HNKPC) models estimated for headline and core inflation in Poland. We analyse the roles of the global vs. domestic output gaps in affecting price changes. We ensure that our conclusions are robust by taking into consideration various proxies for inflation expectations, imported inflation, the domestic output gap and the global output gap. Our results suggest that the global demand conditions are statistically insignificant in the majority of the estimated global versions of HNKPC, independently of the measure of them that is considered. In terms of empirical fit, and especially of the out-of sample forecasting accuracy, the specifications of the Phillips curve with the domestic and global output gaps among the explanatory variables are not superior to traditional Phillips curves. Interestingly, the relative importance of the global output gap is much smaller in models that are estimated in terms of core inflation, excluding foodstuffs and energy, than in CPI inflation models. This suggests that global demand conditions affect the inflation in Poland indirectly, mainly through the prices of food and energy raw materials. The main conclusion from our study is that external factors that are already considered in the traditional hybrid versions of the new Keynesian Phillips curve are sufficient to account for global influences on prices in the domestic economy. The concept of the global output gap improves neither the explanatory nor the predictive power of HNKPC models. (C) 2019 International Institute of Forecasters. Published by Elsevier B.V. All rights reserved.