The EPA window sticker numbers are completely useless. If you want to know real world fuel economy just check fuelly.
2013 Ford C-Max MPG Reports | Fuelly
2013 Ford Fusion MPG Reports | Fuelly
How hard was that? I would eliminate the EPA test all together and calculate each manufacturer's CAFE number based on the previous model year real world fuel economy. All new cars at this point can calculate their own fuel economy in real time and they have a data connection for GPS, streaming music, etc. Use it to report fuel economy in real time in the real world.