What is core inflation?

This paper revisits the question of what core inflation is meant to represent and assesses the competing measures of core inflation that are available, including some new ones. I take the primary perspective that core inflation is a simple predictor of future headline inflation. There is evidence for ex food and energy, and other core measures, being superior predictors than headline inflation itself. Within choices of core inflation, simple averaging of different measures and different horizons seems to work best. I also consider some other concepts of core inflation: closeness to a common trend component and measurement of demand-driven inflation. The averaging estimator fares well by all of these metrics.