In models where both investors and securities are subject to differential taxation, there may be no set of prices that rule out infinite gains to trade, or “tax arbitrage.” This paper characterizes the joint restrictions on financial‐asset returns and investors' tax schedules that preclude tax arbitrage in the absence of short‐sale constraints. The authors show that, if there exists any configuration of marginal tax rates on investors' tax schedules that rule out infinite gains to trade, then “no‐tax‐arbitrage” prices will exist. They also show that the existence of “no‐tax‐arbitrage” prices ensures the existence of equilibrium prices.

In models where both investors and securities are subject to differential taxation, there may be no set of prices that rule out infinite gains to trade, or "tax arbitrage."This paper characterizes the joint restrictions on financial-asset returns and investors' tax schedules that preclude tax arbitrage in the absence of short-sale constraints.The authors show that, if there exists any configuration of marginal tax rates on investors' tax schedules that rule out infinite gains to trade, then "no-tax-arbitrage" prices will exist.They also show that the existence of "no-tax-arbitrage" prices ensures the existence of equilibrium prices. THE EFFECTS OF DIFFERENTIAL taxation on the equilibrium prices of financial assets have attracted much attention from financial economists in recent years.Otherwise identical securities that contribute to taxable income to different degrees will, in general, be valued differently by taxable investors.As a result, tax considerations have been useful in helping explain the effect of dividend yield on stock returns,' the effect of coupon levels and term to maturity on bond prices,2 the timing of investors' portfolio transactions,3 and the observed capital structures of firms.4While a rich set of observed behaviors can be better understood by reference to differential taxation, there are well-known difflculties in dealing with taxes in a general-equilibrium setting.To clear markets, relative prices must reflect the marginal rates of substitution of all agents simultaneously.When tax rates differ across investors, however, this condition can be impossible to achieve.To illustrate, consider a world of perfect certainty with two assets: a tax-exempt municipal bond and a taxable government bond.To equate marginal rates of substitution, the rate of return on the government bond, rg, must equal that on the municipal, rm, "grossed up" by one minus the investor's marginal tax rate, ti; that is, rg = rm/( 1 -ti).If there are investors in more than one tax bracket, this condition will obviously be impossible to satisfy for all of them simultaneously.

The authors' main goal in this paper is to ascertain whether conventional measures of abnormal mutual fund performance are sensitive to the benchmark chosen to measure normal performance. They employ the standard CAPM benchmarks and a variety of APT benchmarks to investigate this question. They find little similarity between the absolute and relative mutual fund rankings obtained from these alternative benchmarks, which suggests the importance of knowing the appropriate model for risk and return in this context. In addition, the rankings are not insensitive to the method used to construct the APT benchmark. Finally, they find statistically significant measured abnormal performance using all the benchmarks. The economic explanation for this phenomenon appears to be an open question.

This paper investigates the month‐by‐month stability of (a) daily returns and correlation coefficients of stock returns, (b) correlation and covariance matrices, (c) number of return‐generating factors, and (d) the APT pricing relationship. The results show that there is a January effect and a small‐firm effect in stock returns. Correlation matrices are more stable than covariance matrices, but both types of matrices are not stable across months and across the sample groups. The number of return‐generating factors is rather stable most of the time and for most of the sample groups, but there is some significant instability that is related to the average correlation coefficients among stocks. The APT pricing relationship does not seem to be supported by the two‐stage process using the maximum‐likelihood factor analysis.