Résumé
The industrial organisation of a food value chain is likely to affect the quality of price transmission between markets. Intermediaries may use a fixed mark-up, hence the proportionality found between prices at different stages, or conversely change the mark-up according to their market power. A large-scale study of various European fish value chains indicates a statistical and amazing relationship between the proportionality of prices and the transmission of price changes upwards. The role of supermarket chains is proposed as a possible explanation of this phenomenon.