SHAREHOLDER LIMITED LIABILITY AND MEAN‐VARIANCE MODELS OF CAPITAL STRUCTURE*
论证股东有限责任对企业借款施加了上限，忽略此限制会导致均值-方差最优资本结构模型的荒谬结论；在考虑公司所得税和无成本破产时，公司价值随债务单调递增直至该上限，从而为在均值-方差框架中引入有成本破产提供了依据。
ABSTRACT This paper demonstrates that shareholder limited liability imposes a restriction on corporate borrowing and that failure to incorporate this restriction into the analysis yields the “reductio ad absurdum” argument against mean‐variance models of optimal capital structure. With corporate income taxes and costless bankruptcy, the firm's value is a monotonically increasing function of debt as long as the amount of debt does not exceed the upper limit imposed by shareholder limited liability. As a result, the introduction of costly bankruptcy into the mean‐variance framework is justified.