12. The IRRC gives dates for some of the provision changes?where available, these data suggest that the majority of the provisions were adopted in the 1980s. Danielson and Karpoff [1998] perform a detailed study on a similar set of provisions and demonstrate a rapid pace of change between 1984 and 1989.
13. Berkshire Hathaway disappeared because it added a second class of stock before 1998. Firms with multiple classes of common stock are not included in our analysis.