The revised Consumer Price Index: changes in definitions and availability.

The release of the January 1987 Consumer Price Index (cpi) in February will introduce updated market baskets that reflect population distributions from the 1980 census of population and spending patterns from the 1982-84 Consumer Expenditure Survey . This release will be part of a 5-year program to update the cpi market basket and incorporate numerous technical enhancements . t Although the cpi is a measure of price change for a market basket of constant quality and quantity, it also needs to retain its relevance to consumers' experience by pricing items currently purchased. New consumer purchasing patterns occur as a result of changes in a number of factors, such as relative prices, income, tastes, demographic characteristics, technological changes, and population shifts . Thus, periodic revisions of the cpi are necessary to incorporate updated versions of the market basket . This article is one of a series that provides detailed information about the cpi revision . It highlights the changes that will occur in the availability and in the definitions of indexes. Many of the changes derive from shifts that have occurred in the spending patterns of the American public . Nearly five decades of spending patterns as reflected in the cpi expenditure weighting patterns and the corresponding relative importance of major groups are shown in table 1 . A later article will discuss the new expenditure weights in detail .