Separate prices and quantities
Gross domestic product measures final production within the United States. Nominal GDP expresses that production at current prices. It can increase because more is produced, because prices rise, or because both occur. Its dollar value alone does not isolate a change in quantities.
Real GDP uses price-adjusted, chain-type quantity measurement to separate changes in production from changes in prices. BEA expresses the level in chained dollars with a stated reference year. The reference year is metadata; it can change during updates and should remain in a downloaded dataset.
Do not add chained-dollar components
Chain-type measures update relative price weights over time. Their chained-dollar components generally do not sum exactly to the total outside the reference-year setting. Adding real consumption, investment and other chained-dollar components is therefore not a valid general method for recreating real GDP.
To describe how a component affects GDP growth, use the producer’s published contributions or a validated method. A component’s own growth rate is not its contribution in percentage points. This site does not create component contribution estimates by casually adding or multiplying incompatible levels.
Levels and growth rates
A quarterly GDP level is commonly presented at a seasonally adjusted annual rate. That level is not the number of dollars produced only during the quarter. Quarterly annualized growth compounds the quarter-to-quarter level ratio over four quarters; it is distinct from nonannualized quarterly change and year-over-year growth.
Advance, second and third estimates can all be followed by further revisions. The third estimate is not permanently final. For research, retain the observation quarter, nominal or real basis, source publication date, transformation and site snapshot. A file fetched today can contain estimates published earlier, so acquisition and publication must remain separate.