Wal-Mart, the largest retailer worldwide, has been suspected of exercising market power over input providers, both merchandise suppliers and workers. However, in spite of a growing body of literature investigating the beneficial economic impact of the company through its price-lowering effect, research analyzing the company’s economic impact over input suppliers is limited. This paper presents a general framework which can be used to investigate Wal-Mart’s market power over input suppliers, vis-à-vis a variation in input productivity, focusing on homogenous intermediate goods supplied locally. The model is general enough to account for incumbents’ reaction to Wal-Mart’s entry resulting in exit, entry and changes in the production technology. A simplified version of the theoretical model is tested using data on local labor markets. Preliminary results show Wal-Mart having a wage lowering effect due mainly to the increased productivity of labor, while the increase in oligopsony power counts only for 15% of such effect.