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.
Penn World Table
A common practice for comparing GDPs across countries has been to use exchange rates. However, this assumes that this relative price - based on traded products - is representative of all relatives prices in the economy, i.e. that it represents the purchasing power parity (PPP) of each currency. By contrast, PWT uses detailed prices within each country for different expenditure categories, regardless of whether the output is traded internationally (say, computers) or not (say, haircuts). These detailed prices are combined into an overall relative price level, typically referred to as the country's PPP. The detailed prices used to compute PPPs are based on data published by the World Bank as part of the International Comparison Program (ICP).