The main purpose of a CPI is to measure changes over time in the general level of prices of goods and services that a reference population acquire, use or pay for consumption. PPIs are used for monitoring price movements of (or deflating output of) specific products or industries. In addition, they are usually aggregated in some way, to provide more general indicators of inflationary pressure.

Individual price indices disseminated by the OECD should be considered as partial indicators as they each relate to a particular segment of economic activity. Each indice has different objectives and use different methodologies in their construction. The selection of the most appropriate measure(s) for any given application is particularly important.

The current international standard for the compilation of CPIs are those adopted by the 14th International Conference of Labour Statisticians in 1987. A comprehensive description of the methodologies for collection price information and compiling these indices is also provided in Consumer Price Indices: An ILO Manual (R. Turvey et al, 1989). A CPI expert group is currently revising this manual.

There are no universally accepted international guidelines and recommendations for the compilation of PPI's. The UN, Manual on Producer's Price Indices for Industrial Goods (1979) only provides a detailed description of methodologies and best practice for the collection of price data and the compilation of PPI's. A PPI expert group, led by the IMF, is currently working on a revised manual.