A number of models developed for asset pricing are two variable models. For instance the Capital asset pricing model (CAPM) developed by Sharpe (1964) considers the risk-free return and volatility of the risk-free return to market return as the determinants of asset price. Asset price as described by CAPM is linearly related to the two independent variables. Many studies have concluded that over the years assets were being underpriced (Smith, 1977; Loderer, Sheehan & Kadlec, 1991) and this raises the question of the adequacy of the various asset pricing models to ensure efficient asset pricing. Brav & Heaton (2003).
