Many researchers use the G-index or E-index to measure firms' takeover defenses. Others argue that these indices are not related to firms' takeover likelihoods. We find that, unlike their raw values, the instrumented versions of these indices are significantly and negatively related to acquisition likelihood. The difference between the raw and instrumented results indicates that the G-index and E-index include an endogenous component and highlights the importance of accounting for endogeneity in tests that use takeover indices to measure takeover deterrence. We provide data on new instruments that researchers can use to address these issues.

We summarize and synthesize the results from 73 studies that examine the consequences of shareholder activism for targeted firms, and draw two primary conclusions. First, activism that adopts some characteristics of corporate takeovers, especially significant stockholdings, is associated with improvements in share values and firm operations. Activism that is not associated with the formation of ownership blocks is associated with insignificant or very small changes in target firm value. Second, shareholder activism has become more value increasing over time. Research based on shareholder activism from the 1980s and 1990s generally finds few consequential effects, while activism in more recent years is more frequently associated with increased share values and operating performance. These results are consistent with Alchian and Demsetz' (1972) argument that managerial agency problems are controlled in part by dynamic changes in ownership, and with Alchian's (1950) observation that business practices adapt over time to mimic successful strategies.

Many researchers use the G-index or E-index to measure firms’ takeover defenses. Others argue that these indices are not related to firms’ takeover likelihoods. We find that, unlike their raw values, the instrumented versions of these indices are significantly and negatively related to acquisition likelihood. The difference between the raw and instrumented results indicates that the G-index and E-index include an endogenous component and highlights the importance of accounting for endogeneity in tests that use takeover indices to measure takeover deterrence. We provide data on new instruments that researchers can use to address these issues.Received April 13, 2016; editorial decision October 14, 2016 by Editor David Dennis.

An extensive literature examines the causes and effects of financial misconduct based on samples drawn from four popular databases that identify restatements, securities class action lawsuits, and Accounting and Auditing Enforcement Releases (AAERs). We show that the results from empirical tests can depend on which database is accessed. To examine the causes of such discrepancies, we compare the information in each database to a detailed sample of 1,243 case histories in which regulators brought enforcement actions for financial misrepresentation. These comparisons allow us to identify, measure, and estimate the economic importance of four features of each database that affect inferences from empirical tests. We show the extent to which each database is subject to these concerns and offer suggestions for researchers using these databases.