In addition to ignoring abnormal earnings beyond year 4, equation (4) imposes two key restrictions. First, it assumes that discount rates (embed ded in the coefficients aT+ 1) are constant across firms. Second, because the coefficient on book value (a 1) is constrained and because that coeffi cient reflects the degree of accounting conservatism (Feltham and Ohlson
1995), the specification assumes that conservatism is either constant
across firms or completely reflected in the form of higher abnormal earn
ings within the forecast horizon.