Efficency

This may be an out there question but...

I was riding home last night on the XC bike (Specialized Stumpy) and i normally ride home on the other bike (Giant OCR Compact road bike) after cursing the hill up to North Sydney while following a commuter and thinking gee the XC bike is inefficent on the road! perhaps a carbon bit here or there would help, harder tyres blah blah blah

I was thinking....

Do manufacturers do some kind of a test where they test the efficiency of a bike, that is, can they put someone one it and work out how much energy is needed to pedal it along at say 30km/hr?? And then as a good consumer we can go buy a bike that is efficent, that we we can cut through all the jargon of carbon this vs 29er that. I mean car manufacturers do a test on aerodynamic efficiency of a car, why not some kind of a power efficiency?

Obviously there are a lot of variables - suspension set up, flex in the frame, cranks tyres etc..

Lorrie