Lucian A. Bebchuk, Alma Cohen & Charles C.Y. Wang, Learning and the Disappearing Association Between Governance and Returns, 108 J. Fin. Econ. 323 (2013).
Abstract: The correlation between governance indices and abnormal returns documented for 1990-1999 subsequently disappeared. The correlation and its disappearance are both due to market participants' gradually learning to appreciate the difference between good-governance and poor-governance firms. Consistent with learning, the correlation's disappearance was associated with increases in market participants' attention to governance; market participants and security analysts were, until the beginning of the 2000s but not subsequently, more positively surprised by the earning announcements of good-governance firms; and, although governance indices no longer generated abnormal returns during the 2000s, their negative association with firm value and operating performance persisted.