The only thing I can think of is they started using fuel injection instead of carburetion - but I would think this would be an improvement. Like some of the others say - it heavily depends on the rider and how the bike is ridden. I ride every day, everywhere I go - and I get 40 - 45. In the very few circumstances I really romp on it - i'd say about 38mpg.
Fuel injection is the way to go in my opinion. Others may say differently, however I am a fan of technology. Carbs become not synchronized, dirty, and very inefficient over time. Fuel injectors are a quick replace, and let a computer take over for fuel management. They're more efficient, more reliable, easier, and cheaper to replace. They require less maintenance, and can be easily retuned should you choose upgrades.
Carbs are old school, some swear by em, some don't. Given the choice of not riding at all versus riding with carbs - I would choose the carbs still. So I don't really have anything terrible against them despite what I say, I just prefer fuel injection.
I hadn't heard anybody mention this yet but I feel like if i recall correctly they went from carburetor to fuel injector around 07 or 08? Same time period you refer to.
