Securities class action filings hit record levels in 2017, driven primarily by lawsuits challenging mergers and acquisitions, according to two prominent studies that came out this week.

Both Cornerstone Research and NERA Economic Consulting found in annual reports that the number of class action filings brought by shareholders last year was the highest since 2008 and, when excluding the IPO craze of 2001, since the passage of the Private Securities Litigation Reform Act in 1995. Cornerstone Research’s report pegged the total at 412, up 52 percent from 2016, and NERA’s review found there were 432 filings, up 44 percent.