Beta alavancado considerando o beta da dívida: a partição de riscos entre acionistas e credores

Abstract

Since Markowitz's (1952) pioneering paper has shown that risk and return must be evaluated simultaneously, with return being the variable to be maximized and risk being the factor to be minimized, investors have sought to control and reduce the risk to which they are exposed. The solution proposed by the author was the diversification of investments where an asset should be evaluated according to the behavior of its covariance among other assets. Following Markowitz's ideas, shareholders should diversify their stock portfolio in order to limit their exposure to risk. But is it possible the risk of shareholders in a single company could be reduced by transferring risk to creditors? This would be feasible considering Proposition II of Modigliani and Miller (1958, 1963) according to which the firm's value is independent of its capital structure. Using the beta index (from the CAPM model, initially developed by Sharpe (1964) from the Markowitz studies) as a good measure of risk, and considering that it is possible to estimate the market value of corporate debt employing the Merton model (1974), in which the shareholders are identified as holders of a call option on the assets of the firm, the beta value of the corporate debt was estimated by calculating the covariance of its return with the return of the market portfolio. Using the Conine (1980) model, a hypothetical situation was simulated to check if there would be a risk transfer between shareholders and creditors. The result was compared to an econometric model where the risk of debt was regressed on the risk of the shareholder and other control variables. The main conclusion of this study was that the shareholder beta index and the corporate debt beta index tend to move in opposite directions, considering the cases where it was possible to apply the Merton model (1974). Therefore, it can be stated that a reduction in shareholder risk tends to increase the risk of creditors.