Federal securities class actions decreased in the first half of 2012 compared with last year largely because of a decline in Chinese reverse mergers and the lowest number of mergers and acquisitions since the third quarter of 2009, according to a study.

According to the Stanford Law School Securities Class Action Clearinghouse and Cornerstone Research, 88 federal securities class-action, or group, lawsuits were filed in the first six months of this year, a reduction of 6 percent from both the first half and second half of 2011.

Stanford Law School and Cornerstone reported five securities class actions filed over Chinese reverse-mergers in the first half of the year, a 79 percent decline compared with the same period last year, and seven such filings related to mergers and acquisitions in the past six months, a 67 percent decline from the same period in 2011.