The researchers noted that litigation activity related to the credit crisis was nearly cut in half, highlighting this as one key driver of the downward trend in filings overall. According to the report, filings related to the credit crisis totaled 100 in 2008, but only 53 in 2009–with only 17 of those 53 filings occurring in the second half of 2009.

Figures contained in the report analyzing filings by sector and by class date reveal that plaintiffs' law firms are generally paying less attention to financial firms–last year's litigation hot spot–but more attention to securities frauds allegedly perpetrated in the distant past.

Contained in the report is a "Litigation Heat Map," a graphic that portrays the intensity of litigation activity within each industry over time. The map shows that nearly one-third, or 32.6 percent, of all financial firms included in the S&P 500 Index were named as defendants in securities class actions filed in 2008, but the figure dropped to just 11.5 percent in 2009.

The financial sector still garnered roughly half of all 2009 securities class action filings, however, with 84 in total.

"Plaintiffs simply ran out of financial firms to sue, and the rising stock market made it harder for plaintiffs to assert claims," said Professor Joseph Grundfest, director of the Stanford Law School Securities Class Action Clearinghouse, commenting on the report in a statement.

The report reveals the increase in "older lawsuits" by measuring the lag between the filing date and the end of class period. Historically, the median lag was 28 days, but it reached 100 days in the second half of 2009, the researchers estimated. In addition, the percentage of filings with more than a year's lag time was 18 percent in 2009, compared to just 5 percent in 2005.

The professor said, "If history is a guide, these lawsuits are more likely to be dismissed and can therefore be characterized as lower quality claims," referring to a finding that 55 percent of filings with more than a year lag have historically been dismissed (over the time period from 1996 to 2006). This compares to a lower 36 percent historical dismissal rate for claims with six-month or shorter lags.

The overall trends revealed in today's Stanford/Cornerstone analysis mirror those separately reported by other researchers in recent weeks, although actual counts differed from one report to the next.

Kevin LaCroix, author of the D&O Diary blog, reported in the Jan. 4 blog entry that he tallied 189 securities class action lawsuits for 2009 and 224 for 2008.

While Mr. LaCroix's description of his method of counting appears to be similar to the Stanford/Cornerstone method–consolidating multiple filings related to the same allegations against the same company–today's Stanford/Cornerstone analysis does not include class actions filed in the last two weeks of 2009.

NERA Economic Consulting in New York reports much higher figures for all years, but overall declines nonetheless. NERA, in a Dec. 15, 2009 report, anticipated 235 cases for the full-year 2009 compared to 253 in 2008.