What Matters in Corporate Governance?
从IRRC的24项条款中筛选出6项构建“管理层防御指数”，发现该指数上升与企业估值下降及负异常回报显著相关，而其余18项条款则无关。
We investigate the relative importance of the twenty-four provisions followed by the Investor Responsibility Research Center (IRRC) and included in the Gompers, Ishii, and Metrick governance index (Gompers, Ishii, and Metrick 2003). We put forward an entrenchment index based on six provisions: staggered boards, limits to shareholder bylaw amendments, poison pills, golden parachutes, and supermajority requirements for mergers and charter amendments. We find that increases in the index level are monotonically associated with economically significant reductions in firm valuation as well as large negative abnormal returns during the 1990--2003 period. The other eighteen IRRC provisions not in our entrenchment index were uncorrelated with either reduced firm valuation or negative abnormal returns. The Author 2008. Published by Oxford University Press on behalf of The Society for Financial Studies. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org., Oxford University Press.