I’m sure you’ve heard the joke before. Q. What’s the difference between a supermarket trolley and a retail analyst? A. The trolley has a mind of its own.

Could the same not also be levelled at the retail industry itself? I’ve observed before how often Tesco copies ideas: from organic veg boxes and advertising straplines to price guarantee websites and own-label products, its mimicry isn’t always clever, but it’s often effective in neutralising competitive advantage.

Yet the truth is, everyone’s at it. Supermarkets are engaged in a space race, even though volumes are declining.

Three of the big four have followed John Lewis in offering a price guarantee, without any obvious increase in sales. Waitrose has just launched a loyalty card, even though Tesco’s reining back the Clubcard points. And Morrisons is seriously contemplating online, while rivals are using stores to subsidise their online custom.

As our columnist Sue Mountstevens says this week, R&D in retail stands for ‘rip-off and duplicate’. Instead of seeking out a point of difference, it’s as if everyone wants to be the same. And somehow better at the same time.

At its results this week, Sainsbury’s cited research to try to measure what would happen if it could neutralise opposition. “If Asda, Tesco, Sainsbury’s and Morrisons all had similar size stores that were equally easy to get to and had the same prices,” it asked in the online survey, “which one would you use?”

Naturally, a lot more shoppers said they would like to shop at Sainsbury’s. And Morrisons and Asda would also see a slight pick-up in trade. Only Tesco would see a decline. And interestingly, a survey by CACI shows 65% of Morrisons customers who shop online do so at Asda.

So that’s bad news for Asda if Morrisons launches a website. In theory. Yet I can’t help thinking this hypothesising is a bit of a waste of time. If all things were equal, I would buy my groceries in Selfridges, while The Grocer’s offi ces would be on the penthouse floor.

But all things aren’t equal. I bought a sausage roll for lunch, and we’re here in Crawley. And after almost 150 years, what keeps us strong is innovation.