European Fuel Economy

Now this's interesting. I'd always heard that European cars in general get higher fuel efficiency than US cars, so I looked it up briefly. Wikipedia, for example, says that a typical European car gets 47 mpg highway, 36 mpg city [Wikipedia: Gas mileage]. But then I checked the Smart Fortwo specifically, since it's got such horrible gas mileage. The exact same model of car the EU rates as 50 mpg while the US rates it as 36 mpg [Wikipedia: Smart Fortwo].

This makes me question our testing methods, and whether European cars really do get better gas mileage than ours. I mean, if we don't test things the same way, it's comparing apples and oranges. Anyone know more about this?