# capital-asset pricing model

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## capital-asset pricing model (CAPM)

## capital-asset pricing model

a share price valuation model in which the major factors of short-term share-price determination are explained. The capital-asset pricing model provides a method of computing the return on a FINANCIAL SECURITY which specifically identifies and measures the risk factor within a PORTFOLIO holding. The expected rate of return on a particular investment has two components:- the risk-free percentage return which could be obtained from, say, a gilt-edged, government financial security;
- the risk return associated with the investment. (Risk itself can be split into market or nondiversifiable risk and specific or diversifiable risk.) This relationship between risk and return is shown in Fig. 15.

The total expected return on an investment is or_{m}, but risk only attaches to non gilt-edged securities which is why the capital market line intercepts the vertical axis at r_{f}. The capital market line shows how, in a competitive market, the additional risk premium varies in direct proportion to β. known as the BETA COEFFICIENT. At point M in the figure there is perfect correlation between movements in the market generally as detailed by an all-share index, and a particular investment. Therefore β= 1 at point M. Where there is no risk, as in Treasury bills, β= 0. β is a measure of market risk because investors have it within their power to diversify away specific risk to almost zero by holding a broad portfolio of shares. It is possible to estimate the beta coefficient of a security from published information.

See also EFFICIENT MARKETS HYPOTHESIS, PORTFOLIO THEORY.