The links between inflation and inflation uncertainty at the longer horizon

In this paper I examine the Okun-Friedman hypothesis of the link between inflation and inflation uncertainty using historical international data on the monthly CPI. An indicator of inflation uncertainty at the two-years-ahead horizon is derived from a time-series model of inflation with time-varying parameters by means of Monte-Carlo simulations. This indicator is compared to other uncertainty measures, with the short forecast horizon and based on simpler GARCH-type models. The analysis convincingly demonstrates that both the longer horizon and changing parameters are important for the regularity. The evidence obtained strongly supports the Okun-Friedman hypothesis both in the time dimension for most countries and across countires.