Définition
GDP can be calculated as the sum of its different components (Σ Ai). Any variation of one of its components has an effect on the growth of the GDP. The contribution of the component Ai to the growth of the GDP between t and t-1 is equal to the growth of component Ai weighted by its weight in GDP at period t-1.
GDP growth may be broken down into the sum of contributions from its various components: household, general government and non-profit institutions serving households consumption expenditure, investments, changes in inventories and trade balance.
In simple cases, aggregates in current prices for example, the contribution of a component to an aggregate (the GDP for example) is equal to the product of that component's growth rate by its weight in the aggregate on the previous period.
With chain-linked volumes at the price of the previous year, a concept of volume according to which the national accounts are published, the previous calculation applies to annual accounts with the growth of the component in chain-linked volume and weight in current prices (the case of changes in inventories is specific). Regarding quartely accounts, due to particularities of chain-linking such a calculation only gives an approximation. The approximation is generally good enough but the contributions obtained are not additive.