The Application of Augmented Fama-French Three Factor Model in Explaining Tehran Stock Exchange’s Firms Return Changes

Fama and French (1993) show that systematic risk of market, size, and book to market value constitute the common risk factors in the United States exchange market. In this study, we examine the explaining power of their model in Tehran stock exchange (TSE) for the period of 1991-2015, and explore the validity of the model in TSE. While book to market value risk is of less importance for investors in TSE, size risk is essential and is priced for a large number of firms. Further, we investigate the contribution of each risk factor in bull and bear markets. It is shown that in bull markets, investors pay more attention to size risk, and in bear markets, risk of book to market value is more important in determining the risk factor. Finally, we introduce risk of price to earning as a common risk factor and add it to Fama-French three-factor model. We emphasize its role alongside the other three factors in stock pricing in TSE.