For a product and if 1 and 2 are the indices of the two years :

– We note, for the producer and for a given year, P the carbon weight of its sales, Q their quantity and p their carbon weight per unit sold ;D the producer’s decarbonation for this product between years 1 and 2.

– For the producer’s inputs (purchases or production emissions/captures) and for a given year, we note the unit weight of input i ; the quantity of input i required to produce one unit sold,

-If, for the product market and for one year, S is the total sales and p is the average unit weight, then we have :