The centenary of the creation of the first self-service supermarket is approaching. 1916 was when the self-service age began with Clarence Saunders opening his bizarrely named Piggly Wiggly stores in Memphis. Others experimented with self-service, but Saunders patented key features. Supermarkets have spread globally ever since. Wherever self-service is applied, that market is revolutionised.

Rewriting our Unmanageable Consumer book this summer, my co-author and I were struck by how consumers are now unpaid workers. Consumers’ purchasing patterns are endlessly studied and forecast, but the modern consumer-as-worker phenomenon has only recently become a subject of inquiry. Back in 1980, US futurologist Alvin Toffler prophesised the advance of the ‘prosumer,’ a producer who is also a consumer. Indeed, food workers everywhere are brand carriers for employers, logo-covered, and incentivised to buy their own products.

“The growth of consumers doing unpaid work is astonishing”

The growth of consumers doing unpaid work for companies is also astonishing. The internet is key to this. Consumers ‘co-create’ by giving the company feedback for free.

They make design suggestions, collect the food, provide back to companies endless information that contributes to marketing. When customers choose which community organisation to support, or when geeks join a hackathon, they work for free.

Academic studies are divided over whether this consumer-worker is a new form of exploitation or is wrenching some creativity out of the soulless task of sitting at a computer, negotiating the internet labyrinth.

Retail analysts know this argument is sensitive. In a market where changes in a few million purchasing acts affect market share, destroy CEOs and, horror of horrors, weaken share prices and brands, consumer feelings matter greatly. Everything changes if consumers realise the ‘bargain’ they bought had meant going to work to buy a car to go to an out-of-town shed. If we shop locally, we regain time, a precious commodity. The moment that penny drops, the revolution that Clarence Saunders began almost a century ago might look history indeed.

Tim Lang is professor of food policy at City University, London