What it means
A company's assets must be paid for by someone, and the balance sheet records who: lenders, who are promised fixed payments and rank first, or owners, who are promised nothing and take what remains. The proportions are the capital structure, usually summarised by ratios such as debt to equity, debt to total capital, or net debt to EBITDA.
The classic analysis starts from the observation that, in a world without taxes, distress costs or information problems, the mix would not matter: the value of the company would depend only on its assets and the cash they generate, and changing the financing would only redistribute that value between lenders and owners. In the real world, three things make the mix matter.
Tax: interest is deductible and dividends are not, so debt carries a tax advantage that increases with the amount borrowed. Distress: as debt rises, the chance that the company cannot meet its obligations rises, bringing costs that range from higher interest rates and tighter covenants through lost customers and suppliers to bankruptcy itself.
Incentives and information: debt disciplines managers by committing cash to interest, but heavy debt can push shareholders towards risky strategies and prevent good investments; issuing equity can signal that managers think the shares are overvalued. The trade-off theory says there is an optimal level of debt at which the marginal tax benefit equals the marginal distress cost, and that the optimum is higher for companies with stable cash flows and tangible assets (utilities, property) and lower for those with volatile cash flows and intangible assets (technology, biotechnology).
The pecking-order theory says that companies do not target a ratio but finance first from retained earnings, then debt, then equity as a last resort, because each step outward signals more to the market and costs more. Observed behaviour contains elements of both.
In practice, boards set capital structure by reference to several constraints: the credit rating they wish to maintain, the covenants lenders will impose, the interest cover and leverage ratios peers maintain, the cash flow headroom needed in a downturn, and the investment programme ahead. They adjust it through the choice of financing for each transaction, through dividends and buybacks (which return equity) and through refinancing.
The cost of capital ties the choice to valuation. The weighted average cost of capital falls as cheaper debt replaces equity, up to the point where the rising cost of both debt and equity from added risk outweighs the benefit.
Minimising the weighted average cost of capital maximises the value of the company's cash flows, which is why capital structure is discussed alongside investment appraisal. For readers of accounts, the capital structure explains much of the difference between two companies' returns to shareholders.
A company financed 70% by debt will show a higher return on equity than an identical company financed 30% by debt when times are good, and a lower one, or losses, when they are bad. Return on equity should therefore always be read with leverage in mind.
In practice
Real-world examples.
Example
A regulated water utility maintains net debt at 60% of its asset base because its revenues are stable and its regulator allows a return on that basis.
Example
A biotechnology company carries no debt because its cash flows are uncertain and its assets are intangible, funding itself entirely with equity.
Example
A private equity buyout finances 65% of the purchase price with debt, relying on the target's cash flow to pay it down over five years.
Think of it
“Capital structure is like deciding how to finance a house-how much to put down versus borrow. The mix affects your costs and risks.
Formula
Calculation
Debt to Equity = Total debt / Total equity
Debt to Capital = Total debt / (Total debt + Total equity)
Net Debt to EBITDA = (Debt minus Cash) / EBITDA
Interest Cover = Operating profit / Interest expense
WACC = E/(D+E) x Cost of equity + D/(D+E) x Cost of debt x (1 minus Tax rate)
Worked example. A company has assets of $100,000,000 generating operating profit (EBIT) of $12,000,000 a year, EBITDA of $16,000,000, and a tax rate of 25%. Its cost of debt rises with leverage. It considers three structures.
Structure 1: no debt. Equity $100,000,000. Cost of equity 9%. WACC 9%. Net profit = $12,000,000 x 0.75 = $9,000,000; return on equity 9%.
Structure 2: debt $40,000,000 at 5%, equity $60,000,000. Cost of equity rises to 10.5% for the added risk. Interest $2,000,000; profit before tax $10,000,000; net profit $7,500,000; return on equity 12.5%. Interest cover 6 times; net debt to EBITDA 2.5. WACC = 0.6 x 10.5% + 0.4 x 5% x 0.75 = 6.3% + 1.5% = 7.8%.
Structure 3: debt $70,000,000 at 8% (lenders demand more), equity $30,000,000. Cost of equity 15%. Interest $5,600,000; profit before tax $6,400,000; net profit $4,800,000; return on equity 16%. Interest cover 2.1 times; net debt to EBITDA 4.4. WACC = 0.3 x 15% + 0.7 x 8% x 0.75 = 4.5% + 4.2% = 8.7%.
Structure 2 has the lowest cost of capital and therefore the highest company value; Structure 3 shows the highest return on equity but a higher cost of capital, because the extra return is more than offset by risk. Downturn test: if EBIT falls 40% to $7,200,000, Structure 1 still earns $5,400,000; Structure 2 earns $3,900,000 with interest cover of 3.6; Structure 3 earns $1,200,000 with interest cover of 1.3, close to breaching a typical covenant of 1.25 times, and one more bad year would put the company in default. The board chooses Structure 2 with a policy of keeping net debt to EBITDA between 2 and 3 times and interest cover above 4.Case study
Seen in the real world.
A listed retailer had for years run with almost no debt, a policy inherited from a founder who distrusted banks. It held $180,000,000 of cash, paid a modest dividend, and earned a return on equity of 8%, below its cost of equity of 10%. An activist investor argued that the balance sheet was lazy: the company could borrow $200,000,000 at 4.5%, return $350,000,000 to shareholders through a special dividend and buyback, and still have net debt of only 1.2 times EBITDA.
The board, wary but persuaded by the arithmetic, agreed a smaller version: $120,000,000 of borrowing and a $250,000,000 return, taking net debt to about 0.8 times EBITDA. Return on equity rose to 14% and the share price rose 20%. Two years later a recession cut EBITDA by 35%; the company's net debt to EBITDA rose to 1.3 times, interest cover remained above 8, and it continued to invest in its stores while two more highly leveraged competitors, at 4 to 5 times, closed shops and one entered administration.
The finance director's retrospective for the board concluded that both the founder and the activist had been partly right: the old structure had wasted capital, the activist's full proposal would have left too little headroom for the downturn that came, and the board's compromise had kept the benefit of the tax shield and the buyback while preserving the ability to act when rivals could not. The company's capital structure policy was written down for the first time: net debt between 0.5 and 1.5 times EBITDA through the cycle, with the range tested against a 35% EBITDA fall.
Watch out
Common mistakes.
- Maximising return on equity by adding debt without recognising that the extra return is payment for extra risk and that the cost of capital may be rising.
- Setting capital structure for good times only. The test is whether the company survives a downturn without breaching covenants or cutting investment.
- Ignoring off-balance-sheet obligations (leases, pensions, guarantees) that lenders and rating agencies count as debt.
Questions
People also ask.
Is there an optimal capital structure?
In theory, the level where the tax benefit of extra debt equals its distress cost. In practice, a range appropriate to the company's cash flow stability, asset base and industry, revisited as circumstances change.
Why is debt cheaper than equity?
Lenders bear less risk because they are paid first and have fixed claims, so they require a lower return; and interest is usually tax-deductible.
How do I compare capital structures across companies?
Use several ratios (debt to equity, net debt to EBITDA, interest cover), adjust for leases and pensions, and compare with peers in the same industry, since appropriate leverage varies widely by sector.
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