New store formats including competition from supercenters (driven by Wal-Mart), warehouse clubs, and mass merchandisers have emerged as a major threat to traditional grocery chains. A key issue in the food retailing sector is to understand how the earnings of employees respond to the evolution of new retail store formats and store organizational characteristics. The elasticity of complementarity for food retailers measures how changes in store size affect use of full-time and part-time employees. The evidence for constant returns to scale suggests that the Hicks elasticity of complementarity is the appropriate measure to assess input substitutability for food retailers. As store size increases the marginal value of labor rises and firms hire more part-time employees, along with a smaller increase in full-time workers.