In the first six months of the year, 235 American troops died in combat zones, while 250 contractor personnel died as well. This was not unexpected, and there were many factors at work to make it so. Combat casualties (mainly for Iraq and Afghanistan) were way down in this period. There are about as many civilian contractors involved out there as there are troops. The military personnel are in much better physical shape, thus much less likely to die from accidents or disease. The contractor personnel spent more time on the road, and vehicular accidents have always been higher in combat zones.
Until 2007, the troops had a casualty rate about three times that of the civilians in Iraq. This included non-combat losses (nearly a quarter of all deaths for troops). But after 2007, the civilian casualty rate went from a third of the military one, to half the military one and then kept going until this year, when it passed the military rate.
Armies have always had civilians along, to perform support functions. The historical term is "camp followers." In times past, the ratio of civilians to soldiers was often much higher, like eight civilians for every one soldier. Only the most disciplined armies (like the ancient Romans at their peak), kept the ratio closer to one to one. But when conscript armies became common in the 19th century, it was suddenly cheaper to replace many of those civilians with conscripts (who were paid a nominal wage and were better disciplined.) Now that armies are going all-volunteer, it's gone back to the old days, where it's cheaper to have civilians perform a lot of support jobs.
When there was a lot of fighting going on in Iraq, it was a lot safer to be a contractor, than a soldier. Until 2007, only 917 contractors had died there, which meant you were three times more likely to get killed if you were in uniform. Most of these civilian contractors worked in the well defended bases, and most of the contractor casualties are among those (about a quarter of the total) who did security or transportation jobs that took them outside the wire. But even those had a lower casualty rate than the combat troops. For the really dangerous work, the troops were used. But working in a combat zone is still dangerous, no matter what your work clothes look like.
Another little discussed (in the mass media) aspect of casualties in Iraq and Afghanistan was that they are much lower than in Vietnam, where you were more than twice as likely to get hurt in combat, and three times more likely to be killed. Even with civilian workers suffering less than half that rate, why take the risk? It's the money. A year in Iraq or Afghanistan pays more than several years of work back home, so recruiting civilians is no problem. But the lower level of training and discipline among these civilians led to more deaths from accidents.