Staffing Industry Analysts today released its list of largest U.S. staffing firms. The annual list includes all 104 staffing firms with $100 million or more in 2012 U.S. staffing revenue.

Combined, these firms generated $66.9 billion in U.S. staffing revenue, which comprised 54.0 percent of the total market. Staffing Industry Analysts predicts that the total U.S. staffing market will reach $139.4 billion in 2014.

The top five largest firms in the U.S. are:

1. Allegis Group, 2012 U.S. staffing revenue $7.71 billion, market share 6.2 percent
2. Adecco, 2012 U.S. staffing revenue $4.38 billion, market share 3.5 percent
3. Randstad Holding, 2012 U.S. staffing revenue $4.15 billion, market share 3.3 percent
4. ManpowerGroup, 2012 U.S. staffing revenue $4.02 billion, market share 3.2 percent
5. Kelly Services, 2012 U.S. staffing revenue $3.46 billion, market share 2.8 percent

“A majority of firms on the U.S. largest list appear to have grown their revenue in 2012 over 2011,” said Timothy Landhuis, research analyst, Staffing Industry Analysts. “Of firms that appeared on both last year’s list and this year’s list, we estimate that these firms’ aggregate revenue grew 6 percent, excluding firms that made a major acquisition. This level of growth is in line with our estimate of 7 percent growth for the total US staffing industry in 2012.”

Landhuis also noted that several firms grew their market share in 2012 as the result of acquiring a comparatively large staffing firm: On Assignment acquired Apex Systems; ACS Group acquired Comforce; TriNet acquired SOI Holdings; and inVentiv Health acquired Kforce’s Clinical Research business.

Corporate members of Staffing Industry Analysts can download the full report by clicking here.