List of countries by GDP (nominal)
Gross domestic product (GDP) is the market value of all final goods and services from a nation in a given year. Countries are sorted by nominal GDP estimates from financial and statistical institutions, which are calculated at market or government official exchange rates. Nominal GDP does not take into account differences in the cost of living in different countries, and the results can vary greatly from one year to another based on fluctuations in the exchange rates of the country's currency. Such fluctuations may change a country's ranking from one year to the next, even though they often make little or no difference in the standard of living of its population.
International Comparison Program
The Program produces internationally comparable price and volume measures for gross domestic product (GDP). Its component expenditures are based on purchasing power parities (PPP's). The International Comparison Program holds surveys collecting price and expenditure data for the entire range of final goods and services at intervals of some few years (the last two were separated by six years). The surveys cover GDPs of countries including their consumer goods, services, government services and capital goods. The ICP tries to make different countries GDPs comparable by calculating them in PPP both currency converters and spatial price deflators.