Transport cost data are obtained as follows:Key informants in each of the 101 hamletswere asked about allmarkets utilized by the inhabitants for selling output,which in many caseswere only intermediate points of sale on theway to Antsirabe. For eachmarket, informationwas gathered on the price per kilogram of porter services (inclusive of in-kind
payments) and of ox-cart transport, depending onwhich was available. If both modes were available, we always took the ox-cart price; human porterage is around 25% more expensive per hour of travel time than is transport by ox-cart. Transport costs are also somewhat higher during thewet season, butwe use prices in the dry seasonwhenmost transport
occurs. For hamlets that do not ship directly to Antsirabe, we construct total costs per kilogramto the finalmarket by summing the costs of each leg of the minimum cost route thereto.