The operation and characteristics of the American securities markets have long been major preoccupations of financial research, especially during the last decade. Particular attention has been devoted to the question of whether there exist investment strategies, or investing entities, capable of producing consistently superior investment performance. The general consensus to date is that few, if any, such success stories are observable. Examinations of the value of professional investment research and counsel ([7] [8] [9] [24]), of the payoff from technical trading rules ([11] [13] [18] [20] [26] [34]), and of the investment results of institutional money management ([15] [29] [25] [28]) have, in almost every instance, provided little indication of performance better than that attainable from a simple passive strategy of buying and holding a randomly selected, well-diversified portfolio of securities, after appropriate adjustments for portfolio risk levels are taken into account. The intensive competition in, and rapid information-digesting properties of, the capital market environment have been cited as explanations ([2] [5] [12]).

This paper examines the hypothesis that investors will sort themselves out into tax-induced ‘financial leverage clienteless’ in which the common stocks of highly levered firms will be held by individuals with low personal tax rates, while the shares of firms with little or no leverage will be held by individuals with high personal tax rates. Although the idea of financial leverage clienteless has appeared in the literature before, the immediate motivation for this investigation is a recent paper by Merton Miller. In that paper he argues that under the current U.S. tax structure, personal taxes will offset corporate taxes such that in equilibrium the value of any individual firm will be independent of its use of debt financing. We extend his analysis to show specifically the way in which financial leverage clienteles would come about in his assumed tax environment. We then conduct some direct empirical tests of the leverage clientele hypothesis. These tests can also be viewed as indirect tests of Miller's new proposition on the irrelevance of capital structures. The results of the tests are mixed: The relationship between corporate leverage policies and investors' tax rates is statistically significant, but its magnitude is less than would be predicted by the theory.