Belying its simplicity and ubiquity, the price tag is a surprisingly recent economic development. For centuries, haggling was the norm, ultimately developing into a system that required clerks and shopkeepers to train as negotiators. In the mid-19th century, however, Quakers in the US began to believe that charging people different amounts for the same item was immoral, so they started using price tags at their stores to counter the ills of haggling. And, as this short video from NPR’s Planet Money explains, by taking a moral stand, the Quakers inadvertently revealed an inefficiency in the old economic system and became improbable pricing pioneers, changing commerce and history with one simple innovation.