The price indices measure the percentage change in the expenditure required to purchase a set basket of products and services, or in the revenue received for a set basket of goods and services. The basket represents patterns of consumption or production, as reflected over a particular time period, which is a base period for each index. The basket includes products and services of unchanging quality and quantity or of equal value, such that the changes in the index reflect price changes only. The price indices include the Consumer Price Index and the producer price indices. The Consumer Price Index measures the percentage change that occurs over time in the expenditure necessary to purchase a set basket of products and services whose prices can be measured regularly/systematically. This basket represents the composition of the households' expenditure. The producer price indices measure the percentage change in products and services that producers sell or purchase; these include output and input indices. The baskets are updated periodically based on international recommendations for updating them.