Before revision:  More importantly, it completely overturns key qualitative predictions of the linear model , such as the absence of endogenous time variation in risk premia and level effects, which is crucial for understanding the link between asset prices and macroeconomic risk .
After revision:  More importantly, it completely overturns key qualitative predictions of the linear model , such as the absence of endogenous time variation in risk premia , a property which is lost with linearization .