of the decade, this difference has increased significantly, with a one-point increase in G associated with a decrease in Tobin's Q of 11.4 percentage points. The results for both stock returns and firm value are economically large and are robust to many controls
and other firm characteristics. We consider several explanations for the results, but the data do not allow strong conclusions about causality. There is some evidence, both in our sample and from other authors, that weak shareholder rights caused poor performance in the 1990s. It is also possible that the results are driven by some unobservable firm characteristic. These multiple causal explanations have starkly different policy implications and stand as a challenge for future research. The empirical evidence of this paper establishes the high stakes of this challenge. If an 11.4 percentage point difference in firm value were even partially "caused" by each
additional governance provision, then the long-run benefits of eliminating multiple provisions would be enormous.Appendix 1: Corporate-Governance Provisions This appendix describes the provisions listed in Table I and used as components of the Governance Index. The shorthand title of each provision, as used in the text of the paper, is given in boldface. These descriptions are given in alphabetical order and are similar to Rosenbaum [1998]. For a few provisions we discuss their impact on shareholder rights or the logic behind their categorization in Table I. Antigreenmail. Greenmail refers to a transaction between a large shareholder and a company in which the shareholder agrees to sell his stock back to the company, usually at a premium, in exchange for the promise not to seek control of the company for a specified period of time. Antigreenmail provisions prevent such arrangements unless the same repurchase offer is
made to all shareholders or approved by a shareholder vote. Such provisions are thought to discourage accumulation of large blocks of stock because one source of exit for the stake is closed, but the net effect on shareholder wealth is unclear [Shleifer and Vishny 1986; Eckbo 1990]. Five states have specific Antigreenmail laws, and two other states have "recapture of profits" laws, which enable firms to recapture raiders' profits earned in the secondary market. We consider recapture of profits laws to be a version of Antigreenmail laws (albeit a stronger one). The presence of firm level Antigreenmail provisions is positively correlated with 18 out of the other 21 firm-level provisions, is significantly positive in 8 of these cases, and is not significantly negative for any of them. Furthermore, states with Antigreenmail laws tend to pass them in conjunction with laws more clearly designed to prevent take
overs [Pinnell 2000]. Since it seems likely that most firms and states perceive ntigreenmail as a takeover "defense," we treat Antigreenmail like the other defenses and code it as a decrease in shareholder rights.