Which military retail innovation, first widely implemented during WWII, revolutionized consumer behavior and later became standard practice in civilian retail environments?

Post Exchange (PX) and Base Exchange (BX) stores have been vital to military morale since their formal establishment. These military retail operations represent one of the oldest and most unique retail systems in America, evolving from simple sutler wagons following troops to sophisticated global retail networks. This poll explores how military retail operations have influenced broader consumer behavior and retail trends throughout American history.

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Self-service shopping (customers selecting their own merchandise without clerk assistance)
Military-specific branded merchandise (precursor to modern brand licensing)
Point-of-sale inventory tracking systems using punch cards
Mail-order catalog services with guaranteed delivery dates