Vassalou, M. (2003). "News related to future GDP growth as a risk factor in equity returns." Journal of Financial Economics 68(1): 47-73.
A model that includes a factor that captures news related to future Gross Domestic Product (GDP) growth along with the market factor can explain the cross-section of equity returns about as well as the Fama-French model can. Furthermore, the Fama-French factors HML and SMB appear to contain mainly news related to future GDP growth. When news related to future GDP growth is present in the asset-pricing model, HML and SMB lose much of their ability to explain the cross-section.