CPI-trim and CPI-median are designed to filter out extreme price changes. CPI-trim removes 40% of the most volatile price movements, while CPI-median focuses on the price change at the 50th percentile.
CPI-common uses a statistical approach to track common price changes across various CPI categories.
The Bank of Canada uses these three measures to guide its efforts in achieving its 2% total CPI inflation target, acknowledging that using a set of measures helps to overcome the limitations of any single one.