Cumulative profit peaks well before the customer list ends

Revenue is usually spread fairly evenly across a customer base. Profit concentrates far more sharply – in a real study of a $40B regional bank's 70,000 commercial relationships, just 0.04% of clients generated 10% of total profit, and 7.56% accounted for 80% of it. Cumulative profit peaks around the top 40–50% of customers, then gives most of it back before settling at 100% for the full base. The instinct is to cut the customers past the peak. That's usually the wrong call: fixed costs don't disappear with the customers who leave – they get reallocated across whoever remains.