Years ago, I read that in the American Civil War, there were almost 10 front-line combat troops for every support person in the rear. In WWI, this ratio had changed-there were now about 3 support troops for every 10 front-line soldiers. In WWII, there were more than 3 support/10 front-line. By the time of Vietnam, there were nearly 5 rear area support personnel for every 10 soldiers. Today? a ratio of 3 support troops for every 1 front line soldier.
from a quick scan from the internet ... not my figures
I'd say your figures are correct for current times except it's more like three contractors for every front line trooper. In Iraq the contractors outnumbered the active duty force.
They cut the active duty force so much that it is the only way to do business these days. The good thing is that most of the contractors were active duty at some point.