The Consumer Price Index (CPI) is a measure that examines the weighted average of prices of a basket of consumer goods and services, such as transportation, food, and medical care. It is calculated by taking price changes for each item in the predetermined basket of goods and averaging them. The Consumer Price Index is a monthly measurement of U.S. prices for most household goods and services. It reports inflation, or rising prices, and deflation, or falling prices. Consumer Price Index (CPI) is a measure of changes in the purchasing-power of a currency and the rate of inflation. The consumer price index expresses the current prices of a basket of goods and services in terms of the prices during the same period in a previous year, to show effect of inflation on purchasing power.