The International Comparison Program (ICP) is a worldwide statistical operation involving some 180 countries. It produces internationally comparable price and volume measures for gross domestic product (GDP) and its component expenditures. The measures are based on purchasing power parities (PPPs). To calculate the PPPs, the ICP holds surveys every five years to collect price and expenditure data for the whole range of final goods and services that comprise GDP including consumer goods and services, government services and capital goods.
PPPs are both currency converters and spatial price deflators. They are used by the ICP to make the GDPs of different countries comparable. Initially, the GDPs are not comparable because they are expressed in national currencies and valued at national price levels. But, after PPPs are applied, the GDPs are converted to a common currency and are revalued at a uniform price level. As a result, differences between the GDPs reflect only differences in the volumes of final goods and services purchased.
The GDP volumes facilitate comparisons of the economic size of countries and, when put on a per capita basis, the economic welfare of their populations. They can also be used to compare the overall productivity and investment potential of countries. Other uses include monitoring the incidence of poverty and tracking progress towards the Millennium Development goals.
The main users of the volume and price measures generated by the ICP are international organizations and regional agencies. There is, however, a growing demand for PPPs from a variety of users at the national level: government agencies, universities, research institutes, public enterprises, private firms, banks, journalists and individuals.
The ICP is organized by region. There are six regions of which all but one are overseen by the ICP Global Office in the World Bank. The remaining region is covered by the Eurostat-OECD PPP Program. This program has a different timetable to that of the ICP but employs compatible methodology. Eurostat and the OECD work closely with the Global Office to ensure that their 46 or 47 countries can be combined in a single comparison with the 110 or so countries of other regions.
Responsibility for the ICP within regions is shared between national and regional agencies. National statistical offices carry out data collection. Regional agencies provide guidance and coordinate data collection and data validation. They also put together and finalize the regional comparisons. Responsibility for ensuring that the regional comparisons can be combined in a world comparison and then combining them rests with the Global Office.
Results of regional comparisons are disseminated by regional agencies. Results of the world comparison are disseminated by the Global Office.