Real versus nominal value (economics)
Gross domestic product (GDP) is a measure of aggregate output. Nominal GDP in a particular period reflects prices which were current at the time, whereas real GDP compensates for inflation. Price indices and the U.S. National Income and Product Accounts are constructed from bundles of commodities and their respective prices. In the case of GDP, a suitable price index is the GDP price index. In the U.S. National Income and Product Accounts, nominal GDP is called "GDP in current dollars" (that is, in prices current for each designated year), and real GDP is called "GDP in [base-year] dollars" (that is, in dollars that can purchase the same quantity of commodities as in the base year).
List of countries by GDP (PPP)
GDP comparisons using PPP are arguably more useful than those using nominal GDP when assessing a nation's domestic market because PPP takes into account the relative cost of local goods, services and inflation rates of the country, rather than using international market exchange rates which may distort the real differences in per capita income. It is however limited when measuring financial flows between countries and when comparing quality of same goods among countries. PPP is often used to gauge global poverty thresholds and is used by the United Nations in constructing the human development index. These surveys such as the International Comparison Program include both tradable and non-tradable goods in an attempt to estimate a representative basket of all goods.