Wednesday 14 January 2009

Portfolio Theory: Beta

Beta

As for beta, it is intended to reveal what part of any “market risk premium” is borne by a particular company’s stock. Beta determines this component of the discount rate estimate for a company’s equity by using various assumptions to compare its stock price gyrations with those of the overall stock market or a market index such as the S&P 500.

A stock whose price is more volatile than the market’s is seen as “riskier” than one whose price gyrates less than the market as a whole. Multiplying this measure of price volatility by a “market risk premium” theoretically expresses the differential risk the particular stock poses. The result is added to the risk-free rate to give a discount rate.

Beta is only potentially useful if stock prices of the subject company and of all components of the market or market index result from investor behaviour that is, collectively, rational. Such conditions of “market efficiency” might substantially occur for some companies in some cases and for some markets or some market segments at some time.


Also read:
  1. Understanding Discount Rates
  2. Risk-free rate
  3. Traditional Method: Discount rate or WACC (I)
  4. Traditional Method: Discount rate or WACC (II)
  5. Modern Portfolio Theory
  6. Portfolio Theory: Market Risk Premiums
  7. Portfolio Theory: Beta
  8. Is the market efficient, always?
  9. Discount Rate Determinations: Summary

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