Gross domestic product
Gross domestic product (GDP) is a monetary measure of the market value of all the final goods and services produced in a period of time, often annually 
GDP (nominal) per capita does not, however, reflect differences in the cost of living and the inflation rates of the countries; therefore using a basis of GDP per capita at purchasing power parity (PPP) is arguably more useful when comparing differences in living standards between nations.
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.