Left on the shelf

Nitish Jain’s new research reveals the extent that supermarket customers disrupt the cycle of food expiry dates – with costly consequences


You’re in your local supermarket to do the weekly food shop. Your shopping list is long – and includes English muffins, organic milk and a punnet or two of strawberries. So here’s a question for you, and please, answer honestly: are you one of a tribe of shoppers who will rummage through the produce on display, whether it’s the freezer aisle or the bakery shelves, searching to find the product you require with the longest amount of time left before it expires? If there’s a litre of milk at the front with three days to go, will you push it aside for the one at the back with five days until it will be rendered past its “best before date”? 

Nitish Jain is Associate Professor of Management Science and Operations at London Business School and co-author of a new research paper – Until Later is Preferred Over Sooner: Multiplicity in Product Expiration Dates and Food Waste in Retail Stores. It looks into consumer habits around food “expiration waste” in multinational supermarkets. 

From an academic perspective, he explains, this paper “provides the first extensive evidence of the extent of ‘multiple date expiration waste’ across multiple product-store combinations”. And within it, Nitish identified a surprising outcome – one you’re likely perpetuating.

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“Consumers choose the fresher product, which should be stocked at the back, behind the same product which is due to expire sooner”

Nitish – who has a PhD in Management Science from INSEAD, and whose research interests focus on global supply chains – found that a large number of supermarket shoppers are indeed “disrupting the flow of best practice”, from the point of view of reducing waste in retail stores, “around food expiry dates”. That’s to say, where a blend of “best before” dates are available, consumers choose the fresher product, which should be stocked at the back, behind the same product which is due to expire sooner. This behaviour, Nitish says, results in waste and can be detrimental to the environment. 

It’s important to note, he adds, that a ‘buy sooner-to-expire produce first’ practice does not imply that total waste, at the societal level, will be reduced: “It’s quite possible that if customers are encouraged to buy the earliest-to-expire product, then waste at customers’ homes may increase – so more of a substitution than reduction.”

Market forces

The research idea came about because of Nitish’s interest in food waste, which he wanted to explore and contribute to – with a view to helping supermarkets reduce theirs. According to government statistics, it’s estimated that supermarkets in the UK wasted around 200,000 tonnes of food, equivalent to over 350 million meals – this costs them around £1 billion per year. 

Nitish’s paper looked at the shopping behaviours of customers across more than 15 million sale transactions at multiple stores, on food products with three to 14 days of shelf-life. “Ultimately,” Nitish says, “we confirmed our hypothesis that the later expiry dates are cannibalising the sooner-to-expire produce and this is resulting in costly consequences.” 

Nitish says it shouldn’t be on customers’ shoulders to “fix a system that isn’t working optimally”. He adds that it’s difficult to put a number on customers who act in this way, but “what we do know, from a supply chain perspective, is that if everybody buys ‘sooner’ rather than searching for ‘later’ expiration dates, it’ll result in a significant reduction in waste at the retail level”. 

It’s difficult to nudge a customer to always purchase food products with a ‘sooner’ rather than ‘later’ expiry date. “If I go into a store in the afternoon to buy strawberries,” he continues, “I won’t buy a pack that will go off that day. I’ll choose another that gives me more time to enjoy them when I want to eat them.” But, Nitish acknowledges, if he were intending to make a smoothie, and the “strawberries were reduced, I’d be tempted to buy one with a sooner expiry date, but it would have to fit with my plans”. 

“Stores need to provide the right incentives that are compatible with customers’ viewpoint,” Nitish says – for example, by reducing the price of strawberries due to go off that day, to encourage people to purchase them. But often customers are swayed as long as it suits their intentions. “Nobody wants unnecessary waste,” Nitish adds, “but at the end of the day, customers care about themselves and what they spend their money on, while supermarkets care about their targets,” he says.

“On average, across the collaborating retailer’s multiple stores, at least 23-24% of expiration waste is down to mixed expiry dates being on the shelves”

Food for thought

Nitish’s paper is timely right now, he explains, because “many food retailers worldwide have committed to the United Nations’ Sustainable Development Goals for halving their food waste by 2030”. The majority of UK supermarkets have publicly committed to reduce their waste by half in that timeframe – and in some cases, such as Tesco, manager bonuses are linked to meeting those targets. “This research paper,” Nitish explains, “provides a methodology to assist managers of supermarkets to ask, how much is being wasted due to this multiple expiry date issue – which is currently an imprecise figure – and provides a calculation for managers to work out where their own in-store efforts should be focused” The paper is essentially an “auditing tool” to help those in charge identify and reduce waste in their stores. “For example, if in a manager’s context, waste, due to multiple expiry dates, is only at the most 2% of the total waste in their store, then such a manager is better off focusing on different drivers of waste in their context. In contrast, if multiple-expiry date waste contribution is at least 20%, then correcting it makes sense.”

On average, across the collaborating retailer’s multiple stores, at least 23-24% of expiration waste is down to mixed expiry dates being on the shelves. “That is what surprised me most significantly during my research,” Nitish admits. “Before I set out to look at this, based on conversations with store managers, I expected the numbers to be single digit, but I was stunned by the extent of the waste that is happening due to this practice, simply because multiple expiry dates are on the shelves at the same time. It was a revelation.”

Most retailers, Nitish explains, are often unaware of the extent of waste as a result of the multiple date exposure in their stores and, thus, are constrained in how to prevent it. The main challenge in measuring it is the inability to record “the remaining life of a sold unit – the difference between when a food time expires and when it is actually sold,” Nitish says. Currently, it’s all about units sold or wasted, which is a basic measure. “It would cost millions of pounds to upgrade the technology to record more valuable information that could reduce food waste.” But he adds that “if supermarkets have a reason to invest, they will.” Nitish goes on to say that the Guardian reported that Tesco UK, in 2016, discarded food equivalent to 119 million meals, which he loosely calculates could have sufficiently fed 3.6% of the UK’s malnourished population of three million people.

"About 60% of the food wasted in the UK could be consumed, reported a climate-action NGO called WRAP"

Shopping around

Nitish highlights, however, that the problem doesn’t lie with expiry dates themselves. Expiry dates on food, he says, are important. “If we get rid of them, in order to reduce this kind of food waste, we’re essentially passing the risk to the customer to make savings” – as they’ll have to make their own decisions when to throw food away. The history of food ‘sell by’ dates is relatively short: it’s widely reported that the information was first added to food wrappers in 1972 by Marks & Spencer as a way to indicate quality and freshness of perishable food. Other supermarkets followed suit. In 1979, the EC Labelling Directive required a date of minimum durability on pre-packaged foodstuff.

The fact that it’s illegal for supermarkets to keep food past its sell-by date, with financial penalties if broken, has been credited with significantly reducing cases of food poisoning over the decades. But it also results in millions of tonnes of food waste, as people throw food away while it’s still edible. Often the estimates for when a food goes off can arguably be conservative, which results in excess waste, Nitish acknowledges. About 60% of the food wasted in the UK could be consumed, reported a climate-action NGO called WRAP. It’s estimated that 250,000 tonnes of waste food could be saved by extending product life by just one day.

“If everybody buys the sooner rather than later expiration dates on the shelves, the waste would be ideal from a retailer’s perspective.” Nitish acknowledges. “It’s the mix of sooner and later dates being exposed to customers at the same time that is the problem.”

Calculation for the future

The big question of course, is will supermarkets have done enough to meet their targets to reduce waste by 2030? This paper should certainly help, Nitish believes, and give managers a way to assess and reduce waste until technological advances make the process more intuitive.

Right now, barcodes in supermarkets don’t record data such as the remaining life of a sold unit, but new barcodes will have the capability to record that essential information. “When advanced barcodes are introduced, my paper and my calculation will not be needed,” Nitish admits.

One challenge for retailers, Nitish says, is that hypothetically, “if a retailer strictly brings later-to-expire units out only when all the sooner-to-expire units are sold, then it risks turning a consumer away.” The psychological effects of near-empty shelves, he continues, combined with the consumer’s idiosyncratic consumption requirements, and the availability of the outside option (a close-by alternative store) can all contribute to the consumer walking away. “Put differently, our findings do not imply that our collaborating retailer can reduce expiry-date waste generation by 22% in half of its stores any time soon.”

So next time you’re in a supermarket, searching for the freshest produce, do remember that there is a benefit to choosing produce that will go off sooner rather than later. The onus for this, Nitish admits, shouldn’t be on the consumer, but it could make all the difference in our collective efforts to reduce waste.

Nitish Jain is Associate Professor of Management Science and Operations


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