Computing additive contributions to growth and other issues for chain-linked quarterly aggregates

Since 2007, the French Quarterly National Accounts use a chain-linking method to measure volumes in replacement of volumes in constant prices of the reference year. This paper gathers 7 years of experience of the Quarterly National Accounts unit on this particular topic. We first recall the annual overlap method used in France in comparison with the one quarter overlap method sometimes preferred in other countries. Based on numerical simulations, we show the distribution of two well-known effects: trend effects when elemental prices have different dynamics and non-additivity. In particular, the variance of these effects increases away from the reference year. We also expose two new reasons to prefer the annual overlap method to the one quarter overlap: first, additive contributions to growth can be computed; second, unpleasant interactions with seasonal and trading day adjustment can be avoided.