The consumer price index (CPI) is used to measure changes in the price level of consumer goods and services. As an indicator of changes in the cost of living, it is susceptible to various types of measurement biases.
This article provides estimates of the size of these biases in the Canadian CPI. It concludes that the rate of increase in the CPI probably overstates the rate of increase in the cost of living by about 0.5 percentage points per year.