A NEW APPROACH TO CAPITAL BUDGETING FOR FINANCIAL INSTITUTIONS

The classic approach to capital budgeting based on the standard Capital Asset Pricing Model (CAPM) says that the hurdle rate (or cost of capital) for any new project or investment should depend only on the riskiness of that investment. Thus, the hurdle rate, and hence the expected value of the investment, should not be affected by the financial policy of the company evaluating the project. Nor should the hurdle rate be influenced by the company's risk management policy, or by the kind of assets it already has on the balance sheet. This article argues that such a “singlefactor” model may be inappropriate for banks and other financial institutions for two main reasons:

• ? it is especially costly for banks to raise new external funds on short notice;
• ? it is costly for banks to hold a buffer stock of equity capital on the balance sheet, even if this equity is accumulated over time through retained earnings.

The single-factor CAPM ignores such costs and, in so doing, understates the true economic costs of “illiquid” bank investments. Illiquid investments require special treatment because they impose risks that, although “diversifiable” by shareholders, cannot be readily hedged by the bank and therefore require it to hold more equity capital. The authors accordingly propose a “two-factor” model for capital budgeting— one in which banks' investment decisions are linked to their capital structure and risk management decisions. One of the key implications of the two-factor model is that a bank should evaluate new investments according to both their correlation with the market portfolio and their correlation with the bank's existing portfolio of unhedgeable risks. The authors describe several potential applications of their model, including the evaluation of proprietary trading operations and the pricing of unhedgeable derivatives positions. They also compare their approach to the RAROC methodology that has been adopted by a number of banks.