Modigliani-Miller Theorem II: Finance and Firm Value
The Modigliani-Miller (MM) theorems, developed by Franco Modigliani and Merton Miller, are cornerstones of modern corporate finance. MM Theorem II, in particular, deals with the relationship between financial leverage (debt) and the cost of equity. It fundamentally argues that in a perfect market, the value of a firm is independent of its capital structure.
This second theorem states that the cost of equity (the return required by shareholders) increases linearly with the debt-to-equity ratio of a company. The intuition behind this is that as a company takes on more debt, the risk borne by equity holders increases. Debt holders have a priority claim on the company’s assets and earnings, meaning that in the event of financial distress, they get paid before shareholders. This added risk compels shareholders to demand a higher return on their investment, effectively increasing the cost of equity.
The theorem can be mathematically expressed as follows:
re = r0 + (r0 – rd) * (D/E)
Where:
- re is the cost of equity
- r0 is the cost of equity for an unlevered firm (a firm with no debt)
- rd is the cost of debt
- D/E is the debt-to-equity ratio
This formula highlights the core principle: the cost of equity (re) is equal to the cost of capital for an all-equity firm (r0) plus a premium that compensates equity holders for the increased risk arising from leverage. This premium is directly proportional to the debt-to-equity ratio (D/E) and the difference between the cost of capital for an unlevered firm (r0) and the cost of debt (rd).
However, the MM theorems rely on several simplifying assumptions, including:
- Perfect capital markets: No transaction costs, taxes, or bankruptcy costs.
- Information symmetry: All investors have access to the same information.
- Rational investors: Investors make decisions based on rational economic principles.
- No agency costs: No conflicts of interest between managers and shareholders.
In the real world, these assumptions rarely hold true. Taxes, bankruptcy costs, and information asymmetry exist, which can influence a firm’s optimal capital structure. For example, interest payments on debt are often tax-deductible, providing a tax shield that can increase firm value. Conversely, excessive debt can lead to increased bankruptcy risk, potentially decreasing firm value.
Despite its limitations, MM Theorem II provides a valuable framework for understanding the relationship between leverage and the cost of equity. It emphasizes that financial leverage does not inherently create value. While leverage can increase the return on equity, it also increases the risk borne by equity holders, ultimately leading to a higher cost of equity. In the absence of market imperfections, these effects offset each other, leaving the overall firm value unchanged. In practical application, it highlights the need to consider the impact of leverage on the cost of capital when making financing decisions.