U.S. securities class actions have soared to a two-decade high, topping levels during the financial crisis, after a landmark January 2016 ruling meant to deter lawsuits in Delaware that accomplish nothing for shareholders sent many lawyers scurrying instead to federal courts.

There were 270 shareholder lawsuits in 2016 accusing companies of making false or misleading statements or concealing bad news about their businesses or mergers, a study released on Tuesday by Cornerstone Research and Stanford Law School shows.