In the US there is the government's General Services Administration (GSA). A company which belongs to this usually (must?) publish their government rates. If you do a google search on "GSA rates" you'll find some of them.

Also, the government publishes their rates, for example here is NASA's

http://nasajobs.nasa.gov/benefits/pay.htm

An experienced aerodynamicist at NASA is probably at the GS-13 level. The average fresh out of college PHD is at GS-11. The actual pay varies on location.

Thanks for the link and the info Martin, it is quite interesting!

Regards