The value of a firm is defined as the sum of the firms debt and its equity$$V=B+S$$The firms management should choose the optimal [[Ratio analysis#Leverage ratios|Debt-Equity]] ratio that makes
If we plot the earnings of a firm against its earnings per share in a levered and unlevered firm, we can see how leverage affects the returns to the investor that the firm provides ![[Pasted image 20240415171152.png|400]]
- Perfect competition
- Firms and investors borrow/lend at the same interest rate
- There is equal access to all relevant information
- No transaction costs
Homemade leverage makes the capital structure of a firm irrelevant. By taking margin to buy shares, or by lending to the firm the payoff of an unlevered firm can be replicated when there are no taxes
![[Pasted image 20240415171538.png]] ![[Pasted image 20240415171550.png]]
Leverages increases the risk and return to stockholders. This can be calculated by using the [[Weighted Average Cost of Capital (WACC)]] equation. Without taxes,$$R_0=\frac{B}{B+S}\times R_B+\frac{S}{B+S}\times R_S$$Multiplying by [[Ratio analysis#Leverage ratios|Equity Multiplier]] on both sides, $$\frac{B+S}{S}R_0=\frac BS R_B+R_S$$Therefore, $$R_S = \frac BS(R_0-R_B)+R_0$$Where
A firms value increases with leverage. This is because debt financing is cheaper as it is a [[Corporate income tax]] write off. $$\text{Cash Flow to Investors} = (\text{EBIT} - R_BB)(1-T)+R_BB = \text{EBIT}(1-T)+R_BBT$$Taking the present value of the second term (
Some increase in equity risk is offset by the increased tax shield by more debt investment. The unlevered cost of equity is given by $$R_S=R_0+\frac BS(1-T)(R_0-R_B)$$Plotting this relationship, ![[Pasted image 20240415173300.png|400]] we find that levered firms pay less in taxes than unlevered firms, and this have a lower cost to raising equity the higher their debt to equity ratio.