You have to remember that most actual employees are white-collar types. Almost anything commoditizable or blue-collar gets sent to contractors.
Also, let's not forget the cost of living in DC.
Also, let's not forget the cost of living in DC.
For the folks misunderstanding that comment:
The link goes straight to at least ten pages of positions with USDA which is located in Beltsville, about 10 miles outside of DC. Bethesda and Rockville, both of which are in the top five, are other also DC suburbs. At a glance there are 300K+ positions in the DMV area, a significant percentage of the 1.3M listed.
Bethesda and Rockville are, for all practical purposes, "DC", as are Beltsville, Suitland, Arlington, VA, and a bunch of other locations that are listed in that data. Segmenting them out is like not considering MIT or Harvard as part of the college scene in Boston because they are in Cambridge, which is just being uselessly pedantic.