The cost of equity capital. A simplification

Modigliani-Miller's theorem, which asserts that corporate financing policy is of no consequence, has been shown to hold true under a set of assumptions which is less restrictive than the original set used by MM. Preceding proofs were based on the theory of general equilibrium. Basically, this paper examines MM's second proposition-the linearity of the cost of equity capital with respect to financial leverage-when dropping a few of their basic assumptions but retaining their assumption about incomplete markets. In particular, this paper relaxes the assumptions that (a) the inflows are perpetual and that (b) the firm's future returns belong to the same risk class. The results of the analysis indicate that the linearity will be sustained. The nature of the financial risk premium (the slope), however, has to be modified.