Entry regulation and social welfare with an integer problem

This paper elaborates on Salop (1979) who showed that the number of firms at free-entry equilibrium is excessive from the viewpoint of social welfare (excess-entry theorem). This paper considers an integer problem of the number of firms entering the market. We find that the excess-entry theorem does not hold true if the marginal production cost is increasing, while it holds true if the marginal production cost is constant. This result warns against the use of the excess-entry theorem for rationalizing entry regulation such as the notorious Japanese Large-Scaled Retail Act restricting the new entry of retailers.