Final answer:
Measuring the weighted average cost of capital on a marginal basis refers to the cost of obtaining additional capital, taking into account the company's debt and equity mix, and is important for investment decisions.
Step-by-step explanation:
The concept of measuring the weighted average cost of capital (WACC) on a marginal basis refers to the cost of raising additional capital, considering the company's capital structure. It looks specifically at the incremental cost of obtaining one more unit of capital after accounting for the mix of debt and equity financing the company uses.
Unlike simply calculating the WACC for all capital raised, the marginal WACC is relevant for new investment decisions as it provides an estimate of the return required on additional funds, or a new project, to be profitable given the current cost structure of the company.