Calculation of value indice (services turnover indices):

The gross turnover indices are calculated at the most detailed level of the French classification of activities : the NAF rev. 2 sub-classes. At this level, the index for month m is calculated by linking the index for month m-12 to the change in turnover between m-12 and m. Business demographics (start-ups, closures, entries and exits, changes in sector of activity) are taken into account on a continuous basis to accurately reflect the economic reality. Restructurings that may affect the sectoral outline of VAT returns are treated separately.

The turnover indices change their base and reference every 5 years, except for the next reference year being 2021 in reason of the particularities of year 2020. The indices now published have a base and reference year of 2015. The average value of the indices is 100 in 2015 (previously 100 in 2010).

Calculation of indices in volume:

The indices of services production at a fine level are defined as the ratio of the turnover index in value to an associated price deflator, specific to the sector. This is done for the different classes in the market services. Once the indices at the finest level of nomenclature are calculated, the indices for higher levels are calculated by aggregation (cf infra). They are disseminated on the INSEE website from the class level. They are calculated since 2005, according to the availability of the prices.

For most of sectors, the deflators used are production price indices in services (PPS). Production price indices in services are produced only quarterly (available at T + 60 days) so they have to be converted to monthly indices thanks to econometric methods. Then, at some point, the quarterly price indices are not yet available. Prices must therefore be predicted, before getting the true indice some months later.

Some sectors do not have a production price index for services. In these cases, we use a consumer price index (CPI), or a price index of production in another service appearing as a good proxy. The Consumer Price Index (CPI) is measured all taxes included, so it is necessary to neutralize VAT rate changes.

Aggregation to upper levels:

The estimation of annual weights is based primarily on gross value added data by industry calculated by the annual national accounts (as for industrial production indices). At the finest levels of the classification, weights are also based on INSEE's Esane statistics (structural business statistics).

The 2015 rebasing implements an innovation, with the introduction of a two-weighting system (instead of a constant-weight system) in order to better take into account the structural evolutions. Until now, aggregation of elementary indices was done on the basis of constant weights representing the reference year -- i.e. 2010 previously. From now on, 2010 weights are used for the aggregation of elementary indices between 2005 (respectively 1999 for turnover indices) and 2012, whereas 2015 weights are used for the period after. The calculation on the whole period is then achieved by chaining both series (computation of a link coefficient on the year 2013). This change responds to a recommandation of Eurostat in order to increase the robustness of indices over a long period.