On the Equivalence between the APV and the wacc Approach in a Growing Leveraged Firm
提出一个简单模型，评估增长企业中的税收节省，证明在特定假设下调整现值（APV）与加权平均资本成本（WACC）方法等价，并揭示增长情境下WACC公式隐含的贴现率不一致问题。
Abstract While in a steady state framework the choice between the wacc approach ( Modigliani‐Miller, 1963 ) and the adjusted present value (APV) approach ( Myers, 1974 ) is irrelevant since the two approaches provide the same result, however, in a growing firm context the wacc equation seems to be inconsistent with the APV result. In this paper we propose a simple model to evaluate the tax savings in a growing firm in order to show under which assumptions the two approaches lead to the same results. We demonstrate that the use of the wacc model in a steady‐growth scenario gives rise to some unusual assumptions with regard to the discount rates to be used in calculating tax shields. We show that the widely used wacc formula, if used, as it is in most cases, in a growth context, implies that a) debt tax shield related to already existing debt are discounted using k d ; b) debt tax shield related to new debt, due to company's growth, are discounted, according to a mixed procedure, using both k u and k d . We discuss the inconsistency of such a discounting procedure and the preferred features of the APV approach.