Définition
A composite index number measures the variation in the value of a composite number defined as the aggregate of a set of elementary numbers (for example, the consumer price index measures the variation in the prices of 1,000 varieties of products in a single index number).
The composite index number is a weighted mean of the elementary index numbers in which the weighting represents the "mass" of the elementary numbers (in the case of price indices, this mass is expenditure).
A Laspeyres index is weighted according to mass in the base period.
A Paasche index is weighted according to mass in the current period.