Which military retail innovation from WWII later became a standard practice in civilian customer loyalty programs?

Post Exchanges (PX) and their naval counterparts (NEX) have been vital to military morale since their inception. These retail operations have evolved from simple trading posts to sophisticated retail networks that follow military personnel worldwide. This poll explores how military retail systems pioneered customer loyalty programs that would later influence civilian retail practices.

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Ration card point systems that tracked purchase history and rewarded efficient use
Combat zone price matching guarantees for essential supplies
Military scrip currency that earned bonus purchasing power over time
Unit-based bulk purchasing discounts that increased with deployment length