In recent years, many central banks have adopted inflation targeting policies starting an intense debate about which measure of inflation to adopt. The literature on core inflation has tried to develop indicators of inflation which would respond only to ''significant'' changes in inflation. This paper defines a measure of core inflation as the common trend of prices in a multivariate dynamic model that has, by construction, three properties: it filters idiosyncratic and transitory macronoises, and it leads the future level of headline inflation. The paper shows that the popular trimmed mean estimator of core inflation could be regarded as a proxy for the ideal GLS estimator for heteroskedastic data. It employs an asymmetric trimmed mean estimator and obtains an unconditional measure of core inflation.
