A decrease in Chinese reverse merger filings, and a move by plaintiffs attorneys to file merger and acquisition objection lawsuits in state rather than federal court, led to a 19.2% drop in federal securities class actions filed last year, according to the Stanford Law School's Securities Class action Clearinghouse, in a report issued Wednesday.

But the Dodd-Frank Act's whistle-blower provisions could lead to an increase in the future, according to a commentary on the report.

There was a total of 152 actions filed in 2012, compared with 188 in 2011, according to the Palo Alto, Calif.-based clearinghouse, which prepares its report in cooperation with Boston-based Cornerstone Research. The total was 21% below the annual average of 193 filings made between 1997 and 2011, and the second lowest total in 16 years.

Trends discussed in the report include:

• Federal filings associated with merger and acquisition transactions fell to 13 in 2012, compared with 40 and 43 in 2010 and 2011 respectively, with evidence indicating these actions are now being pursued almost exclusively in state courts.

• The rush of filings against Chinese issuers listed on U.S. exchanges through reverse mergers has subsided, decreasing to a total of 10 in 2012 — most of which were filed in the first half of the year — compared with 31 filings in 2011.

• The wave of credit crisis-related filings is over.

• Filing activity in the second half of 2012, at a total of 64, was considerably slower than the 88 filed in the first half of the year.

• There has been an increase in recent years in the percentage of filings in which Rule 10b-5 claims were made. This is a Securities and Exchange Commission-established rule that allows insiders of publicly traded firms to set up a trading plan for selling their own stock.

“What stood out in 2012 was the absence of a filing trend that influenced the total number of new cases,” Cornerstone Senior Vice President John Gould said in an analysis released with the report.

“In the past, there have been observable filing types, such as (initial public offering) cases, options backdating, mergers and acquisitions, or most recently, Chinese reverse mergers. But 2012 was not dominated by any such trend.”

"Is there a shoe waiting to drop?” asked Joseph Grundfest, director of the Stanford Law School Class Action Clearinghouse, in a statement. “The SEC claims that the Dodd-Frank bounty program has helped it build a large inventory of high-quality leads as to fraud at publicly traded corporations. But will the Commission be able to transform these leads into quality enforcement actions? And, will private-party plaintiffs be successful in prosecuting “piggyback” claims that copy the Commission’s complaints? The current quiet patch in private securities fraud litigation could certainly be unsettled if the Dodd-Frank bounty program generates a new wave of private claims.”

Copies of the report are available here.