CPI Trimmed is a measure of core inflation that excludes CPI components whose rates of change in a given month are located in the tails of the distribution of price changes. This measure helps filter out extreme price movements that might be caused by factors specific to certain components. In particular, CPI-trim excludes 20 percent of the weighted monthly price variations at both the bottom and top of the distribution of price changes, and thus it always removes 40 percent of the total CPI basket.