The Consumer Price Index (CPI) is a measure of the average change in prices over time in a fixed market basket of goods and services. The Bureau of Labor Statistics publishes CPI’s for two population groups: (1) a CPI for All Urban Consumers (CPI-U) which covers approximately 89 percent of the total population and (2) a CPI for Urban Wage Earners and Clerical Workers (CPI-W) which covers 28 percent of the total population.