The article presents a historical review of the literature related to the empirical problem of excessive risk premium. The risk premium (the difference between the return on equities and risk-free rate) observed in financial markets cannot be reconciled with theoretical models of financial...

We report strong evidence that changes of momentum, i.e. "acceleration", defined as the first difference of successive returns, provide better performance and higher explanatory power than momentum. The corresponding Γ-factor explains the momentum-sorted portfolios entirely but not the reverse....