And notice that they say the average is between 10 and 12 mph yet they're comfortable stating a 10% drop. Wouldn't a 10% drop of 12 mph only be 10.8? Still above the their huge average range.
Problems with statistics, much? 
Agreed, also wind farms are strategically placed, it isn't as if they put them in "average" places or for that matter only in the Mid-West. Also Wind turbines work at optimum efficiency when they are in the 20-30 mph of wind range. Many people don't realize that when winds hit a certain range (usually above 50 mph) they have to be shut down. So really they are looking for good wind consistency, not overall high winds.
Oh and someone was talking about the myth regarding wind farms and birds... In actuality the average wind turbine takes out less birds in a year than an american domestic cat (yeah, it really was not as much of an issue as had been previously thought).
