The Arbitrage Pricing Theory (APT) is much more robust than the capital asset pricing model for several reasons:
The APT makes no assumptions about the empirical distribution of asset returns. CAPM assumes normal distribution.
The APT makes no strong assumption about individuals’ utility functions (at least nothing stronger than greed and risk aversion).
The APT allows the equilibrium returns of asset to be dependent on many factors, not just one (the beta).
The APT yields a statement about the relative pricing of any subset of assets; hence one need not measure the entire universe of assets in order to test the theory.
There is no special role for the market portfolio in the APT, whereas the CAPM requires that the market portfolio be efficient.
The APT is easily extended to a multi-period framework.
Since APT makes fewer assumptions than CAPM, it may be applicable to a country like Kenya. However, the model does not state the relevant factors. Cho(1984) has, however, shown the security returns are sensitive to the following factors: Unanticipated inflation, Changes in the expected level of industrial production, Changes in the risk premium on bonds, and Unanticipated changes in the term structure of interest rates
Security returns depend on only three riskfactors-inflation, industrial production and the aggregate degree of risk aversion. The risk free rate is 8%, the required rate of return on a portfolio with unit sensitivity to inflation and zero-sensitivity to other factors is 13.0%, the required rate of return on a portfolio with unit sensitivity to industrial production and zero sensitivity to inflation and other factors is 10% and the required return on a portfolio with unit sensitivity to the degree of risk aversion and zero sensitivity to other factors is 6%. Security i has betas of 0.9 with the inflation portfolio, 1.2 with the industrial production and-0.7 with risk bearing portfolio—(risk aversion)
Assume also that required rate of return on the market is 15% and stock i has CAPM beta of 1.1
Compute security i's required rate of return using
Using APT Ri = 8% + (13% - 8%)0.9 + (10% - 8%)1.2 + (6% - 8%)(-.7)
Using CAPM Ri = RF + (E(RM) - RF)ßi
Ri = 8% + (15% - 8%)1.1 = 15.7%