The eminence of risk-free rates in portfolio management: a South-African perspective

Abstract

The traditional Capital Asset Pricing Model (CAPM) suggests that the minimum return required by an investor should be equal to the return of a risk-free asset (Reilly & Brown, 2003), which should be stable (Reilly & Brown, 2006), not influenced by external factors (Harrington, 1987), and certain (Bodie, Kane & Marcus, 2010). Evidence, however, suggests that risk-free asset returns vary (Brunnermeier, 2008), and that "there is really no such thing as a truly riskless asset" (Brigham & Ehrhardt, 2005:312). The pioneering studies of Mehra and Prescott (1985) and Weil (1989) only justified the size of the equity premium and risk-free rate puzzle but failed to provide a consensus on the specifications for the most ideal risk-free rate proxies. The results from this paper accentuated the problem of selecting a risk-free rate proxy, as all proxies under evaluation exhibited a level of risk and volatile returns. No regularities between the pre-, during and post-financial crisis regarding the choice of most ideal risk-free rate proxy were found. Overall findings suggested that the ideal proxies are the 3-month T-Bill rate and the 3-month NCD rate for the pre-, during and post-financial crisis periods, respectively.