Knowledge that Transforms

The potential performance of an asset set may be obtained by choosing the portfolio proportions to maximize the Sharpe (1966) performance measure. If a portfolio has a Sharpe measure equivalent to the potential performance of the underlying set of assets, then it is efficient. Multivariate statistical procedures for comparing potential performance and testing portfolio efficiency are developed and then evaluated using simulations. Two likelihood ratio statistics are then used to compare stock and bond indices against sets of 20 and 40 portfolios. The procedures are also compared to the Gibbons (1982) methodology for testing financial models.

In his article Determinants of Corporate Borrowing, Myers (1977) says that it is not guaranteed that the maximum value of the firm is reached before the maximum value of the debt is utilized in the case in which the interest payment is fully tax deductible, but the tax shield is lost if the firm goes bankrupt. I have shown here that even in such a case the maximum value of the firm will always be achieved before the maximum available debt is utilized.

The purpose of this paper is to reexamine Reinganum's study which indicates that abnormal returns could not be earned unexpected quarterly earnings information, and to document precisely the response of stock prices to earnings announcements. This study, using a very large sample of stocks and daily returns, represents the most complete and detailed analysis of quarterly earnings reports that has been performed to date. Our results are contrary to those of Reinganum and show that abnormal returns could have been earned almost any time during the 1970's. Our analysis also indicates that risk adjustments matter little in this type of work. Finally, we find that roughly 50% of the adjustment of stock returns to unexpected quarterly earnings occurs over a 90-day period after the earnings are announced.