While TEKsystems continued its 13-year reign at the top of the Largest IT Staffing Firms in the U.S. list, On Assignment captured the second position, boosted by its acquisition of Apex Systems. 

Publicly traded On Assignment acquired Apex Systems, one of the largest and fastest-growing privately held information technology staffing firms in the U.S. in May 2012. Richmond, Va.-based Apex had posted revenue of about $700 million in 2011 and was No. 6 on the Largest IT Staffing Firms in the U.S. list. On Assignment was ranked No. 14 on the list with $238 million in IT staffing in 2011. On Assignment replaced Randstad Technologies, which is now ranked third. 

TEKsystems, which is part of the Allegis Group, is by far ahead of the rest when it comes to market share. With $2.82 billion in 2012, the company claimed 12 percent of the $22.7 billion U.S. IT staffing industry in 2012. On Assignment with $1.08 billion and Randstad Technologies with $1.06 billion in 2012 IT staffing revenue were at a distant second and third positions, respectively, with 5 percent of market share.

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Among the rest of the top 10 in the U.S., IT staffing landscape remained pretty much the same with some minor movements. Adecco slipped from No. 4 to No. 8 position, Insight Global moved up to No. 6 rank from No. 8 and Recruit is now at No. 9, up from No. 12 last year.

Overall, the market share of the top 15 IT staffing firms in the U.S. increased by an average of 1.2 percentage points per year from 2007-2012, while the market share of the top five firms increased by an average of +0.5 percentage points per year. As with other segments, in 2009 market shares of the largest firms jumped up from 2008 levels.

For our complete 2013 Book of Lists, which includes the 32 largest IT staffing firms in the U.S., as well as 25 other staffing firm lists, click here.