The underlying idea is that investors require a rate of return from their resources – i.e. equity – under the control of the firm's management, compensating them for their opportunity cost and accounting for the level of risk resulting. This rate of return is the cost of equity, and a formal equity cost must be subtracted from net income. Consequently, to create shareholder value, management must generate returns at least as great as this cost. Thus, although a company may report a profit on its income statement, it may actually be economically unprofitable; see Economic profit. It is thus possible that a value deemed positive using a traditional discounted cash flow (DCF) approach may be negative here. RI-based valuation is therefore a valuable complement to more traditional techniques.
The equation for EVA shows that there are three key components to a company's EVA: NOPAT, the amount of capital invested and the WACC. NOPAT can be calculated manually but is normally listed in a public company's financials. Capital invested is the amount of money used to fund a specific project. WACC is the average rate of return a company expects to pay its investors; the weights are derived as a fraction of each financial source in a company's capital structure. WACC can also be calculated but is normally provided as public record.
In equity valuation, residual income represents an economic earnings stream and valuation method for estimating the intrinsic value of a company's common stock. The residual income valuation model values a company as the sum of book value and the present value of expected future residual income. Residual income attempts to measure economic profit, which is the profit remaining after the deduction of opportunity costs for all sources of capital.