The Problem with Averages

We reason using averages when the full distribution is what matters — the average obscures critical variation that completely changes the right decision.

• A man drowns crossing a river that is, on average, three feet deep — the middle was ten feet deep.
• Average income is a deeply misleading measure in unequal societies — a handful of billionaires pull the mean far above the median experience.
• A drug that 'works on average' may harm most patients dramatically while producing spectacular results in a small group — the average erases the distribution.