In what decade was the first commercially viable self-checkout system introduced to retail stores?

The retail landscape has been transformed by numerous technological innovations over the decades. One particularly significant development changed how customers complete their shopping experience, reducing wait times and labor costs for retailers. This innovation began in a specific decade and has since become ubiquitous in supermarkets and retail stores worldwide. Test your knowledge about this retail technology milestone that forever changed the customer checkout experience.

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1980s (David R. Humble's invention at Sylvania)
1970s (IBM's early retail automation project)
1990s (NCR's first TouchPath system)
2000s (Amazon's initial automated checkout technology)