Variance and lower partial moment betas as bases for costing equity capital among regulated utilities

An important question in the setting of public utility rates is, 'What constitutes a fair rate of return or cost of equity capital for a regulated utility?' Recent debates over this issue have centred on the CAPM's ability to produce realistic equity cost figures for use in the rate-setting process. Several researchers recommend modified or expanded versions of the market model as a means of improving its predictive capabilities. One such approach is the lower partial moment model. The purpose of the present paper is to assess the robustness of the lower partial moment model relative to the conventional CAPM as a basis for estimating the cost of a utility company's equity capital. The hypothesis that empirical estimates of the LPM beta tend to overestimate the true systematic risk of utility companies was corroborated by our test results.