By Andrew Longstreth

NEW YORK, Jan 14 (Reuters) - Private antitrust lawsuits filed in federal courts rose for the first time in three years, according to statistics compiled by the judiciary's administrative arm.

During the 2012 fiscal year, which ended Sept. 30, antitrust lawsuits rose to 677, up 50 percent from 452 in the previous fiscal year.

Before 2012, antitrust lawsuits had been falling since 2008, according to statistics compiled by the Administrative Office of the United States Courts. Plaintiffs' lawyers attributed the drop to the increasing costs of bringing lawsuits and to the 2007 Supreme Court decision known as Bell Atlantic Corp v. Twombly that made it harder for lawsuits to survive motions to dismiss.

It's unclear what accounted for the increase last fiscal year. Robert Lande, a professor at the University of Baltimore School of Law who specializes in antitrust, cautioned against reading too much into the numbers. He said the increase may be the result of plaintiffs' lawyers filing similar lawsuits for different classes of plaintiffs.

"There are a million different factors to consider," said Lande.

Another gauge of the strength of private antitrust litigation is the number of multidistrict proceedings that consolidate similar lawsuits across courts nationwide.

The number of multidistrict proceedings has been trending downward over the last six years. Reuters has previously reported that multi-district lawsuits consolidated in U.S. district courts dropped to four in 2010, down from 12 the previous year. In 2012, there were six cases tagged as multi-district proceedings, according to data available on Westlaw, a Thomson Reuters database.

(This story has been corrected to reflect that antitrust lawsuits rose by 50 percent, not 33 percent.)

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