An index is used to compare economic data, typically price or quantity against a base value. Specifically, the Consumer Price Index is used to measure changes in prices of a bundle of goods and services over different periods of time for consumers. It covers a variety of goods and services that the BLS consolidated into 8 groups. These groups are food and beverages, housing, apparel, transportation, medical care, recreation, education and communication, and other goods and services. It can be used to measure inflation through change in consumption. The CPI can somewhat be used to measure cost-of-living but does not include governmental or environmental factors and so cannot be viewed as a complete cost-of-living index.