Himmelberg et al. (J. Financial Econom. 53 (1999) 353–384) argue that fixed effects estimators should be used in examination of the relationship between managerial ownership and firm performance. I show that managerial ownership, while substantially different across firms, typically changes slowly from year to year within a company. With rational managers maximising long-term utility, small, one-year changes in ownership are not likely to reflect notable changes in incentives that would lead to substantive within-year changes in performance. By relying on within variation, fixed effects estimators may not detect an effect of ownership on performance even if one exists.