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). Example Real interest rates As was shown in the section above on the real growth rate, where is the rate of increase of a quantity in real terms, is the rate of increase of the same quantity in nominal terms, and is the rate of inflation, and as a first-order approximation, In the case where the growing quantity is a financial asset, is a nominal interest rate and is the corresponding real interest rate; the first-order approximation is known as the Fisher equation. Looking back into the past, the ex post real interest rate is approximately the historical nominal interest rate minus inflation. Looking forward into the future, the expected real interest rate is approximately the nominal interest rate minus the expected inflation rate. Cross-sectional comparison Not only time-series data, as above, but also cross-sectional data which depends on prices which may vary geographically for example, can be adjusted in a similar way. For example, the total value of a good produced in a region of a country depends on both the amount and the price. To compare the output of different regions, the nominal output in a region can be adjusted by repricing the goods at common or average prices. See also Aggregation problem Classical dichotomy Constant Item Purchasing Power Accounting Cost-of-living index Deflation Financial repression Fisher equation Index (economics) Inflation Inflation accounting Inflation hedge Interest Money illusion National accounts Neutrality of money Numéraire Real interest rate Real prices and ideal prices Template:Inflation – for price conversions in Wikipedia articles Notes References (Adam Smith's early distinction vindicated) External links DataBasics: Deflating Nominal Values to Real Values from Federal Reserve Bank of Dallas CPI Inflation Calculator from U.S. Bureau of Labor Statistics Inflation Valuation (finance)