Lumpy curves

Jay Grieves points out that average is a little deceptive.

Outliers can change everything. One Bill Gates raises the average net worth of people at a conference by a whole bunch. Or as Zig Ziglar says, one foot in ice water and one foot in nearly boiling water means that on average, you're just fine.

The secret of thinking about average is to pick the right group. When you have a true bell curve, then you can start to figure out which slice you want.