The real law of averages

If you want to raise the standards of any group, improving the top of the heap isn't nearly as effective as focusing your effort on the base instead.

Simple example: Getting a Prius to go from 50 miles per gallon to 55 miles per gallon isn't nearly as important as getting SUVs to go from 10 miles per gallon to 15. There are two reasons for this. The first is that there are a lot more SUVs than Priuses. The second is that they use far more gallons, so a percentage increase has far more yield. (You can't average averages).