Nonclassical demand: A model-free examination of price-quantity relations in the Marseille fish market

We suggest a model for a market, the Marseille wholesale fish market, in which purchases do not correspond to standard competitive demand. We use nonparametric methods to detect the properties of price-quantity relations which reveal ‘strategic demand’. Our data over three months include price quantity details of each transaction for each fish, and the identities of the buyers and sellers. The observed distributions of prices are stable over time, thus the market can be treated as a repeated game. Strategic demand curves are obtained by local fitting. They are downward-sloping at the aggregate level but not in general at the individual level. Thus regularities are generated by aggregation rather than derived from individual behaviour.