A New Measure for Core Inflation Based on Generalized Dynamic-Factor Model

Many central bankers pay attention to measures for core inflation when deciding how to adjust policy from meeting to meeting even though their statutory targets are set in terms of headline inflation. It is because what central bankers are truly concerned with is underlying inflation going forward. For example, while the official target is set in terms of headline CPI inflation, the Bank of Korea considers a variety of core inflation measures. However, those core inflation measures are somewhat volatile and do not provide a reliable signal of medium-term underlying inflation. Continuing inflation in oil and food prices causes headline CPI inflation rate to deviate from core inflation measures for an extended period of time. In order to provide a clearer picture of underlying inflation pressures to policy makers, we need to develop a new core inflation measure that tracks underlying inflation more closely. Consistent with the current objective of the Bank of Korea that is based on headline CPI inflation, we review several core inflation measures that have been used or proposed by various authors - including those currently used by the Bank of Korea - and propose a new core inflation measure that is based on generalized dynamic-factor modeling. We discuss the behavior of our proposed core inflation measure starting in the 1990s and show that it performs better than the conventional core inflation measures that are currently used.