We build an equilibrium model to explain why stock return predictability concentrates in bad times. The key feature is that investors use different forecasting models, and hence assess uncertainty differently. As economic conditions deteriorate, uncertainty rises and investors' opinions...

We develop a model of firm learning in volatile markets with noisy signals and test its predictions using historical German data. Firms' forecasts improve with age. We exploit German Reunification as a natural experiment where firms in the East are treated with ignorance about the distribution...