Market adjustment with advection and diffusion in excess demand

Although it is extremely rare for real markets to adjust excess demand through the Walrasian tâtonnement, the standard in market adjustment theory, it is also true that excess demand is eventually eliminated. This gap suggests that some other factors, besides the price mechanism, contribute to adjusting excess demand. We hypothesize that consumers and firms, and therefore excess demand, spill over into neighboring markets in response to price differences that arise between markets. This motion must contribute to ameliorating excess demand. It is rational for some consumers (firms) to shift to markets where the prices of commodities are lower (higher) if price differences arise beyond those due to the characteristics of the commodities. Furthermore, excess demand fluctuates depending on the actions of consumers and firms. Thus, we study an economy in which excess demand advects and diffuses owing to price gradients. The application of partial differential equations is appropriate for this type of analysis.