ืIn this section we present and demonstrate the optimum procedure for selecting portfolios when the single-index model is accepted as the best way to forecast the covariance structure of returns.
First we present the ranking criteria that can be used to order stocks for selection for the optimum portfolio. We next present the technique for employing this ranking device to form an optimum portfolio, along with a logical explanation for why it works. while an technique for forming optimum portfolios is easy to understand, the formal proof that it leads to the same portfolio that would be produced by the optimum procedure