Friday, September 17, 2010

FACTOR MODELS AND THE ARBITRAGE PRICING THEORY

Arbitrage Pricing Theory

Arbitrage - arises if an investor can construct a zero beta investment portfolio with a return greater than the risk-free rate
If two portfolios are mispriced, the investor could buy the low-priced portfolio and sell the high-priced portfolio
In efficient markets, profitable arbitrage opportunities will quickly disappear

*Note: we will explore more of this with derivatives later

Figure 7.5 Security Line Characteristics




APT and CAPM Compared
APT applies to well diversified portfolios and not necessarily to individual stocks
With APT it is possible for some individual stocks to be mispriced - not lie on the SML
APT is more general in that it gets to an expected return and beta relationship without the assumption of the market portfolio
APT can be extended to multifactor models

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