Securities class action filings remained at near record levels last year, as public companies faced a greater threat of being sued than in any previous year, according to a prominent report released on Wednesday.

Cornerstone Research, which is based in San Francisco, found in its annual report that plaintiffs filed 403 new federal class action securities cases in 2018, down just 2 percent from a record high of 412 in 2017. However, core filings—which do not include cases stemming from mergers and acquisitions—ticked up to a total of 221 last year, the study found.

According to the report, one in 11 companies on the S&P 500 was sued in 2018, with firms in the health care sector being the prime target of new core filings. About 4.5 percent of companies listed on U.S. exchanges were hit with core filings in 2018, marking the sixth consecutive year that firms' exposure to the claims had increased. Including M&A filings, a record 8.4 percent of U.S. exchange-listed companies were sued last year, the report found.

The findings followed another report from NERA Economic Consulting on Tuesday, which noted an increase in settlement values last year had coincided with an uptick in securities class action filings. NERA's report pegged the total number of filings at 441 for 2018, up slightly from the year before.

Cornerstone, which partnered with the Stanford Law School Securities Class Action Clearinghouse, found that the 403 federal securities class actions filed last year were the second-highest on record, trailing only 2017. The volume of core filings in 2018 was the highest since 2008, when the financial crisis hit and filings surged due to volatility in the U.S. and global financial markets, the report found.

Meanwhile, filings stemming from mergers and acquisitions decreased to 182 in 2018 from 198 the year prior, but still registered the second-highest total since Cornerstone began separately tracking core and M&A filings in 2009. The study found that the Delaware Court of Chancery's 2016 rejection of disclosure-only settlements in Trulia had resulted in more merger-objection lawsuits being filed in federal courts, with courts in the Second and Third Circuits fielding nearly half of all filings in 2018.

The Cornerstone review found that three law firms—The Rosen Law Firm and Pomerantz, both in New York, and Los Angeles-based Glancy Prongay & Murray—were driving the increase in core filings over the last six years, though their rate of appointment as lead or co-lead counsel had not changed in recent years.

In total, Rosen, Pomerantz and Glancy Prongay accounted for 54 percent of all core filings in 201, and were appointed lead counsel in a little more than 40 percent of all cases. They were typically picked to lead cases whose size were smaller than the national average, Cornerstone said.

The firms, however, were also responsible for more individuals being named as lead plaintiff in core securities filings, reversing a trend from 2004 to 2012 when large institutional investors were more likely to play that role, according to the report.

“Starting in 2013, individuals were appointed as lead plaintiff more often than institutional investors. This suggests a shift in litigation strategies by some plaintiff law firms,” it said.