Which retail innovation, introduced in 1916, fundamentally transformed shopping behavior and became the foundation of modern supermarkets?

Throughout history, retail innovations have dramatically transformed how we shop and consume products. From ancient marketplaces to modern digital platforms, these innovations have not only changed business models but also shaped cultural and social behaviors. This trivia challenges you to identify a revolutionary retail innovation that fundamentally altered the industry landscape in the 20th century.

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Self-service shopping (Piggly Wiggly's innovation allowing customers to select their own merchandise without clerk assistance)
The shopping cart (invented by Sylvan Goldman for his Humpty Dumpty supermarket chain)
Barcode scanning (developed by IBM for automated checkout)
Department store catalog (pioneered by Montgomery Ward as 'wish books')