In this thesis, regulatory effects on uniform pricing and two part pricing by a multiproduct monopoly are examined and compared. In each pricing system, pricing policies and regulatory effects are seen to depend on whether products are complements or substitutes. The behavior of multiproduct monopoly maximizing profit differs from a purpose of regulator maximizing social welfare. This thesis explores two regulatory remedies, which are rate of return regulation and price cap regulation. When products are complements, in two part pricing the regulations decrease the social welfare, but in uniform pricing the regulations increase the social welfare only if two markets have similar market sizes. When products are substitutes, the regulations increase social welfare only if two markets have similar sizes of capital capacities.
