Examining Pareto Law across department store shoppers.

This article examines the contribution and stability of "heavy buyers"—the top 20% of customers by transaction frequency and value—in an East Asian department store chain using over 550 million loyalty program transactions across three years. Findings reveal that these heavy buyers account for 71% of total revenue and 52% of transactions at the store level, with their contribution varying significantly across departments (65% to 86% of department revenue). The stability of heavy buyers over time also differs widely by department, ranging from 11% to 74%, indicating the need for department-specific retention strategies. Additionally, the study applies the Duplication of Purchase Law to show that heavy buyers in one department are about three times more likely to be heavy buyers in other departments, which has implications for managing cross-department promotions and resource allocation. These insights highlight the nuanced application of Pareto Law in retail and suggest tailored loyalty and marketing approaches within multi-department stores.