A Reconsideration of Tax Shield Valuation
纠正了在恒定杠杆政策下，对自由现金流折现和加权平均资本成本计算的常见误解，推导出税盾估值的一般结果，并给出了永续和任意现金流的正确估值公式。
A quarter-century ago, Miles and Ezzell (1980) solved the valuation problem of a firm that follows a constant leverage ratio L = D/S. However, to this day, the proper discounting of free cash flows and the computation of WACC are often misunderstood by scholars and practitioners alike. For example, it is common for textbooks and fairness opinions to discount free cash flows at WACC with beta input β S = [1 + (1 − τ)L]βu, although the latter is not consistent with the assumption of constant leverage. This confusion extends to the valuation of tax shields and the proper implementation of adjusted present value procedures. In this paper, we derive a general result on the value of tax shields, obtain the correct value of tax shields for perpetuities, and state the correct valuation formulas for arbitrary cash flows under a constant leverage financial policy.