Department of Defense Contractor and Troop Levels in Iraq and Afghanistan: 2007-2017 [April 28, 2017] [open pdf - 726KB]
From the Document: "This report provides background information for Congress on the levels of Department of Defense (DOD) troop and contractor personnel deployed in support of prior and ongoing military operations in Iraq and Afghanistan. [...] Throughout its history, DOD has relied on contractors to support a wide range of military operations. Operations over the past 30 years have highlighted the critical role that contractors play in supporting U.S. troops-both in terms of the number of contractors and the type of work being performed. During recent U.S. military operations in Iraq and Afghanistan, contractors frequently averaged 50% or more of the total DOD presence in-country."
CRS Report for Congress, R44116
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html