Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
We use the cross-section regression approach of Fama and MacBeth (1973) to construct cross-section factors corresponding to the time-series factors of Fama and French (2015). Time-series models that use only cross-section factors provide better descriptions of average returns than time-series models that use time-series factors. This is true when we impose constant factor loadings and when we use time-varying loadings that are natural for time-series factors and time-varying loadings that are natural for cross-section factors.Authors have furnished an Internet Appendix, which is available on the Oxford University Press Web site next to the link to the final published paper online.