【文章內容簡介】 and cumdividend price scaled by the dividend, to try and measure clientele effects. If the price declines by the full amount of the dividend, after the payment of the dividend, the dropoff ratio is one. Elton and Gruber report a positive association between the mean dividend yields and dropoff ratios. They interpret this as being consistent with the existence of a tax clientele effect and infer the marginal tax rates of investors from the size of the dropoff ratio. The implication is that shares with a larger dropoff ratio possess a clientele of investors with a lower tax burden on dividends received. Kalay (1982) has argued that it is not possible to infer investor clientele tax rates from the size of the dropoff ratio. This is because dropoff ratios would be bounded by transactions costs, not marginal tax rates. A paper by Clarke, in this volume, assesses the impact of a change in tax regime on dropoff ratios in a sample of Australian shares resulting from the switch to a dividend imputation tax system in July 1987. However, these differences were not statistically significant and the large amount of noise in the data makes it difficult to draw clear cut conclusions. Further evidence relating to the impact of changes in dividend taxation regimes on security prices and yields is provided by Poterba and Summers (1984). They analyse a sample of British share price data for a period from 1955 to 1981. 4. Agency costs and dividend policy Jensen (1976) demonstrate that if management serve their own interests and not those of outside shareholders, then agency costs could arise. These will result because shareholders forsee that managers can increase their own wealth at their expense by the excessive use of perks or by shirking. In the Jensen and Meckling (1976) scenario, ownermanagers may find it optimal to incur monitoring and bonding costs to reduce potential agency costs. These agency costs take a number of forms including monitoring costs and excessive risk aversion by managers who have a significant portion of their own wealth tied up with the fortunes of the firm. Unduly conservative behaviour may serve the interests of the firm39。s creditors but not the shareholders. Rozeff (1982) suggests that in the absence of taxes, it is possible for a firm to have an optimal dividend policy due to the existence of agency costs. He argues that dividend payout ratios could be conditioned by a tradeoff between the flotation costs of raising external finance and the benefit of reduced agency costs, realised when the firm increases its dividend payout ratio. Easterbrook (1984) also suggests that dividend payments may serve to reduce agency costs. Management can change the risk of the firm by changing both the profile of its real investment projects and the relative balance of debt and equity. By maintaining a constant payment of dividends it avoids a build up in the balance of equity funds and simultaneously forces the firm to seek external finance. The raising of external finance will cause periodic reviews of the firm39。s activities by the contributors of capital。 their presence therefore eases the burden on existing shareholders. Shareholders will also benefit from the adjustment of leverage ratios which will acpany the raising of external finance. This argument also provides a potential explanation of why panies pay dividends and raise external financ