During the dotcom era, there were predictions of the Dow Jones Index soaring to 30,000. But this was a time when the market lost itself to the hype. When investors, along with their valuations, come back down to earth from such heights, there can be a loud thump, reminding everyone that it's time to get back to fundamentals and take a look at a key aspect of share valuations: the weighted average cost of capital (WACC).
Understanding WACC
The capital funding of a company is made up of two components: debt and equity. Lenders and equity holders each expect a certain return on the funds or capital they have provided. The cost of capital is the expected return to equity owners (or shareholders) and to debtholders, so WACC tells us the return that both stakeholders  equity owners and lenders  can expect. WACC, in other words, represents the investor's opportunity cost of taking on the risk of putting money into a company.
To understand WACC, think of a company as a bag of money. The money in the bag comes from two sources: debt and equity. Money from business operations is not a third source because, after paying for debt, any cash left over that is not returned to shareholders in the form of dividends is kept in the bag on behalf of shareholders. If debt holders require a 10% return on their investment and shareholders require a 20% return, then, on average, projects funded by the bag of money will have to return 15% to satisfy debt and equity holders. The 15% is the WACC.
If the only money the bag held was $50 from debtholders and $50 from shareholders, and the company invested $100 in a project, the return from this project, to meet expectations, would have to return $5 a year to debtholders and $10 a year to shareholders. This would require a total return of $15 a year, or a 15% WACC.
WACC: An Investment Tool
Securities analysts employ WACC all the time when valuing and selecting investments. In discounted cash flow analysis, for instance, WACC is used as the discount rate applied to future cash flows for deriving a business's net present value. WACC can be used as a hurdle rate against which to assess ROIC performance. It also plays a key role in economic value added (EVA) calculations.
Investors use WACC as a tool to decide whether to invest. The WACC represents the minimum rate of return at which a company produces value for its investors. Let's say a company produces a return of 20% and has a WACC of 11%. That means that for every dollar the company invests into capital, the company is creating nine cents of value. By contrast, if the company's return is less than WACC, the company is shedding value, which indicates that investors should put their money elsewhere.
WACC serves as a useful reality check for investors. To be blunt, the average investor probably wouldn't go to the trouble of calculating WACC because it is a complicated measure that requires much detailed company information. Nonetheless, it helps investors know the meaning of WACC when they see it in brokerage analysts' reports.
Calculating WACC
To calculate WAAC, investors need to determine the company's cost of equity and cost of debt. Here's a breakdown:
Cost of Equity
The cost of equity can be a bit tricky to calculate as share capital carries no "explicit" cost. Unlike debt, which the company must pay in the form of predetermined interest, equity does not have a concrete price that the company must pay, but that doesn't mean no cost of equity exists. Common shareholders expect to obtain a certain return on their equity investment in a compIany. The equity holders' required rate of return is a cost from the company's perspective because if the company does not deliver this expected return, shareholders will simply sell their shares, causing the price to drop. The cost of equity is basically what it costs the company to maintain a share price theoretically satisfactory to investors. On this basis, the most commonly accepted method for calculating cost of equity comes from the Nobel Prizewinning capital asset pricing model (CAPM): Re = Rf + Beta (RmRf). But what does that mean?
 Rf – Riskfree rate  This is the amount obtained from investing in securities considered free from credit risk, such as government bonds from developed countries. The interest rate of U.S. Treasury Bills is frequently used as a proxy for the riskfree rate.
 ß – Beta  This measures how much a company's share price reacts against the market as a whole. A beta of one, for instance, indicates that the company moves in line with the market. If the beta is in excess of one, the share is exaggerating the market's movements; less than one means the share is more stable. Occasionally, a company may have a negative beta (e.g. a goldmining company), which means the share price moves in the opposite direction to the broader market. (Learn more in Beta: Know The Risk.)
For public companies, you can find database services that publish betas of companies. Few services do a better job of estimating betas than BARRA. While you might not be able to afford to subscribe to the beta estimation service, this site describes the process by which they come up with "fundamental" betas. Bloomberg and Ibbotson are other valuable sources of industry betas.
 (Rm – Rf) = Equity Market Risk Premium  The equity market risk premium (EMRP) represents the returns investors expect to compensate them for taking extra risk by investing in the stock market over and above the riskfree rate. In other words, it is the difference between the riskfree rate and the market rate. It is a highly contentious figure. Many commentators argue that it has gone up due to the notion that holding shares has become more risky.
The EMRP frequently cited is based on the historical average annual excess return obtained from investing in the stock market above the riskfree rate. The average may either be calculated using an arithmetic mean or a geometric mean. The geometric mean provides an annually compounded rate of excess return and will in most cases be lower than the arithmetic mean. Both methods are popular but the arithmetic average has gained widespread acceptance.
Once the cost of equity is calculated, adjustments can be made to take account of risk factors specific to the company, which may increase or decrease company's risk profile of the company. Such factors include the size of the company, pending lawsuits, concentration of customer base and dependence on key employees. Adjustments are entirely a matter of investor judgment and they vary from company to company. (Learn more in The Capital Asset Pricing Model: An Overview.)
Cost of Debt
Compared to cost of equity, cost of debt is fairly straightforward to calculate. The rate applied to determine the cost of debt (Rd) should be the current market rate the company is paying on its debt. If the company is not paying market rates, an appropriate market rate payable by the company should be estimated.
As companies benefit from the tax deductions available on interest paid, the net cost of the debt is actually the interest paid less the tax savings resulting from the taxdeductible interest payment. Therefore, the aftertax cost of debt is Rd (1  corporate tax rate).
Finally – Capital Structure
The WACC is the weighted average of the cost of equity and the cost of debt based on the proportion of debt and equity in the company's capital structure. The proportion of debt is represented by D/V, a ratio comparing the company's debt to the company's total value (equity + debt). The proportion of equity is represented by E/V, a ratio comparing the company's equity to the company's total value (equity + debt). The WACC is represented by the following formula: WACC = Re x E/V + Rd x (1  corporate tax rate) x D/V.
A company's WACC is a function of the mix between debt and equity and the cost of that debt and equity. On one hand, in the past few years, falling interest rates have reduced the WACC of companies. On the other hand, the spate of corporate disasters like those at Enron and WorldCom have increased the perceived risk of equity investments. (Learn more in Evaluating A Company's Capital Structure.)
Be warned: the WACC formula seems easier to calculate than it really is. Just as two people will hardly ever interpret a piece of art the same way, rarely will two people derive the same WACC. And even if two people do reach the same WACC, all the other applied judgments and valuation methods will likely ensure that each has a different opinion regarding the components that comprise the company value.

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