Economists often assume that agricultural markets in history were competitive, and all producers received the same price. In contrast, most agricultural historians deem prices to differ among agents, according to their social status and «power». This paper tests these opposite views with a database of some 12,500 transactions for the São Paulo area in Brazil in the first decades of the 19th century. Prices received by farmers were positively related to total sales, a proxy for the size of the estate, and also to the share on the relevant market, which measures the market power. These results are consistent with the anecdotal evidence about the growing importance of large slave estates which, however, did not wipe out small household farms.
