Over the 197789 period, the productivity gains in agriculture have enabled the prices of agricultural products to fall in real terms, giving an advantage to the customers. An application of the method of "surplus accounts" to the datas of National Accounts allows analysing transfers of purchasing power by prices between the different economic agents. Generally speaking, the food industries have properly transmitted these price changes to their selling prices. On the opposite, the trading sector have distributed them only imperfectly. The gap between production prices and retail prices is very often due to the increase of trade margins
