Variations in levels of embodied technology generated variations in English plough prices in 1770. Using plough prices as a quality index, this article explains size and daily output of plough teams. It shows that variations in plough technology were due to technological change?not static optimization?and village plough technology was influenced by neighbouring villages. But technological advance was not constrained on the demand size: farmers purchased the best ploughs available. Rather, local supply of technology was the limiting factor. Technological change, urbanization, and information networks are rejected as explanations of local supply of technology. The key factor was market density.