中文摘要：

前期文献从一般意义上检验了税率变动对企业资本结构调整行为的影响，但忽略了破产成本这一重要因素。本文从节税收益与破产成本权衡的角度重新审视了这一问题。理论分析表明，由于债务悬置效应的存在，面临税率的外生变化，企业的资本结构调整行为具有非对称性。这是因为当企业因为税率变动而调整负债率时，虽然边际节税收益为常数，但边际破产成本却是递增的。这意味着面临同样的税率变化，高负债企业和低负债企业的表现可能迥异。我们的经验分析支持上述理论预期。研究发现低负债率企业的资本结构对税率上升更为敏感，而高负债率企业则对税率下降更为敏感。本文深化和拓展了税收与资本结构理论的研究，也对认识税率调整下企业的财务行为具有一定的实践意义。

英文摘要：

Previous studies investigate the impacts of tax rates changes on capital structure adjustment, condi- tional on a fixed bankruptcy costs, thus can provide only limited evidence to the trade off theory. This paper re- investigates this question with a careful consideration of the trade off between the tax shield benefits and bank- ruptcy costs during the process of capital structure adjustment. Theoretical analysis shows that when the debt o-verhang effects are considered, firms may adjust their capital structure asymmetrically as tax rates change. The reason is that, when firm raise debt ratio as tax rates rise, the marginal tax shield benefit is a constant, but the marginal bankruptcy costs rise convexly. This implies, given the same degree of tax rate change, firms with high leverage may act differently relative to those with low leverage. We provide evidence this argument. The results show that, high leverage firms are more sensitive to the increase of tax rates, while low leverage firms are more sensitive to the decrease of tax rates. Our results contribute to the tax and the capital structure literature, and have important practical significance to understand the financing behavior of the corporate under the adjust- ment of tax rate.