Arbitrage pricing theory is between one of two influential economic theories of how assets are formed or priced in the financial markets and the other model is the capital asset pricing model. Arbitrage pricing theory states that the price of a financial asset reflects a few key risk factors, like as the expected rate of interest & how the asset price changes relative to the price of a portfolio of assets. If price of asset happens to diverge by what the theory states it must be arbitrage by investors should bring it back into line.