Allegis Group, Randstad and ManpowerGroup Inc. (NYSE: MAN) ranked as the three largest suppliers of information technology staffing in the U.S., according to Staffing Industry Analysts’ 2012 list of largest U.S. IT staffing firms released this week.

Allegis’ TEKsystems division ranked as largest overall with market share of 13 percent. It was followed by Randstad Technologies with market share of 5 percent and ManpowerGroup’s Experis division with market share of 4 percent.

Overall, this year’s list of largest IT staffing firms included 33 companies, up from 31 on last year’s list. The 33 largest firms on the 2012 list had combined revenue of $13.0 billion and 63 percent market share.

“The majority of firms on the list achieved double-digit revenue growth in 2011, underscoring the immense demand for information technology staffing," said Research Analyst Timothy Landhuis.

"As technology increasingly undergirds more and more business processes, staffing agencies that can supply IT talent will continue to benefit from this trend," Landhuis said. "We project that the market for information technology staffing in the U.S. will grow by 14 percent in 2012 to reach $23.5 billion."

To make the list of largest IT staffing firms, companies had to have at least $100 million in U.S. staffing revenue in 2011. As a note, Staffing Industry Analysts ranked companies by revenue, according to industry custom, but this ranking should not be taken to imply that a firm with a higher rank provides better service or more value to its shareholders.

Corporate members of Staffing Industry Analysts can access the full list by clicking here.