Around 25% of consumers shop at both Sainsbury’s and Asda where the two supermarkets are in close proximity, research has revealed.

Location data analysis from Retail Economics and mobile location specialist Location Sciences revealed the overlap in the grocery giants’ customer bases as the duo press on with plans to merge in a £13bn mega deal.

Sainsbury’s shocked the market at the end of April by detailing plans for a £13bn tie-up, which would create an enlarged business capable of toppling grocery market leader Tesco and competing with online titan Amazon.

When presenting details of the merger to the City, Sainsbury’s boss Mike Coupe insisted the two supermarket giants were “strong, differentiated brands” with “distinctive propositions”, which appeal to different customer bases.

Sainsbury’s, Coupe said, appealed to customers wanting “great fresh food”, while Asda was the preferred destination for consumers hunting “fair prices”.

In their analysis of 75,000 consumers in five postcodes that contain both a Sainsbury’s and an Asda, Retail Economics and Location Sciences found that an average of 25% of people shopped at both retailers during March.

That percentage rose to 35.1% in Bexleyheath and 27.4% in Charlton Riverside.

However, it dropped to just over a fifth in South Ruislip (21.3%) and Monks Cross in York (21.8%).

Location of storesAsda loyalty index
(monthly visits per customer)
Sainsbury’s loyalty index
(monthly visits per customer)
Consumers who shop at both

South Ruislip,




Charlton Riverside,








RH10 1EG




Monks Cross,
YO32 9LG




The five locations are among those that will fall under the microscope of the Competition and Markets Authority (CMA) in its investigation into the deal.

The CMA will assess competition and market share at hyper-local levels, focusing its attention on stores that are within a 12-and-a-half minute drive of each other.

Sainsbury’s and Asda have asked the competition watchdog to fast-track that probe to a phase-two investigation.

Retail Economics chief executive Richard Lim said: “The interests of consumers will need to be at the forefront of the CMA’s regional analysis to ensure localised competition remains fierce and brings about the best deal for shoppers.

“It appears inevitable that the combined retail group will be forced to divest some stores as the CMA will be forced to make some tough decisions.

“In the short term, this could be a good opportunity for the other incumbent grocers and the German discounters to snap-up prized locations.”

Location Sciences boss Mark Slade said: “Mapping the historic journeys that shoppers take enables us to understand footfall traffic at a far more granular level and to develop a loyalty index for each brand.

“For Sainsbury’s and Asda, the respective loyalty for each brand is very similar, with shoppers visiting the stores two to three times per month on average.

“The overlap, particularly in key retail locations, is however pronounced, with over 25% of consumers shopping at both supermarkets.”

That could prove a key statistic as the CMA assesses the deal.