I estimated the cost of equity using the capital-asset-pricing model (CAPM). Other methods, such as the dividend-discount model (DDM) and the earnings-capitalization ratio, can be used to estimate the cost of equity. In my opinion, however, the superior method.
My estimate of Nike's cost of equity is 10.5%. I used the current yield on 20-year Treasury bonds as my risk-free rate, and the compound average premium of the market over Treasury bonds (5.9%) as my risk premium. For beta, I took the average of Nike's betas from 1996 to the present.