Each position consists of elementary indices taken now from official statistics.

The weights of the positions and the elementary indices forming the various positions are fixed for the duration of the base.

The positions are calculated through an aggregation - chaining technique of Lowe : the evolution of the position is a weighted average of changes in the elementary indices forming the position.

The businesses and the local communities can use these official indices for construction works contracts, by choosing the activity the closest to the object of their market. These "indices" are constituted as parametric formulas for costs developments on various inputs, as recommended in the guide "The prices in Public Procurement" published by the Legal Affairs Directorate of the Ministry of Economy and Finance in April 2013 ( version 1.1 ). However, other more suitable parametric formulas are permissible, such as the use of " miscellaneous expenses " and " transport" published among the " various index construction " positions ;

The indices BT and TP are disseminated during the third month following the month under review, on the site of the BDM in the theme "Prices and price indices" under " Construction producer price and costs indices", under "Producer cost indices for construction (contract escalation)".

They are also published in the Official Journal.