I analyzed customer purchase data for 14 months across three retail chains, and the 80/20 rule holds almost perfectly — 21% of shoppers generate 79% of revenue. But I'm not convinced that focusing only on that top fifth is smart; the middle tier shows way more growth potential when you look at their month-over-month change. Should we really double down on the loyal high-spenders, or is there more value hiding in the middle of the distribution?