More than 8% of U.S. public companies were hit with a shareholder class-action suit in 2017, a nine-year high.
The 43% increase in securities cases to 270 last year largely reflects "forum shopping" in the wake of a Delaware court ruling.
Plaintiff filings in federal courts are up 17%, and as many as 6% of S&P 500 companies could be the target of such suits this year.
