作者：ERICKSON, G; JACOBSON, R
摘要：We explore the extent to which R&D and advertising expenditures generate a comparative advantage that allows firms to earn supranormal profits. After controlling for unobserved firm-specific factors and the feedback between discretionary expenditures and profitability, our results suggest substantially lower accounting and stock market returns to R&D and advertising than indicated in previous research. Isolating mechanisms, which prevent imitation, do not appear sufficient for either R&D or ad...
作者：KAPLAN, EH; HERSHLAG, A; DECHERNEY, AH; LAVY, G
作者单位：Yale University; Yale University; Northwell Health; North Shore University Hospital; Cornell University; Yale University
摘要：The performance of in vitro fertilization-embryo transfer (IVF-ET) programs is summarized typically as the average probability of achieving pregnancy per cycle. Variation in conception probabilities across women reduces the usefulness of such an aggregate measure. More relevant is the conditional probability of achieving pregnancy on a given cycle following a number of failed IVF-ET attempts. We construct a model that accurately describes 1,257 treatment cycles performed at Yale over 571 diffe...
