Agricultural price volatility is "bad". But where does it come from? Remedies are completely different for "endogenous" or "exogenous" fluctuations. The recent crisis seems to indicate that exogenous remedies have been applied to endogenous fluctuations.

The present study which started in 1999 is framed in the INCOYAM project. Marketing systems of yam are analyzed in three West- African countries: Cote d'Ivoire, Benin and Nigeria. Surveys have been carried out on urban (wholesales and retailers) and rural (collectors) traders. Cities and...