This article is based on research by Marco Bertini and Julia von Schuckmann (Esade), Arjen van Lin (Tilburg University), Aylin Aydinli (Vrije Universiteit Amsterdam) and Erica van Herpen (Wageningen University)

With global supply chains threatened as never before by a combination of extreme climate events and transport restrictions, it is increasingly important to tackle the global problem of wasted food. Some 821 million people in the world go hungry, while in developed nations up to a third of perfectly edible food – 1.3 billion tons of it – ends up spoiled and uneaten.

Most of this waste occurs in our homes. People buy food, presumably with the intention of eating it, and then end up throwing much away.

We can only change this behaviour if we first understand its causes. There is a popular assumption that retailers encourage over-purchasing through discounts and multi-buy deals such as the famous "buy-one-get-one-free" (BOGOF). Supermarkets face criticism for these marketing tactics because, although they may motivate shoppers to buy more than they intended, they may also motivate them to buy more than they need, which presumably results in waste.

But is this intuition accurate? What does the data say?

People buy food, presumably with the intention of eating it, and then end up throwing much away (Photo: Evelien/Twenty20)

Esade researchers Marco Bertini and Julia von Schuckmann partnered with Netherlands-based university associates Arjen van Lin (Tilburg University), Aylin Aydinli (Vrije Universiteit Amsterdam), and Erica van Herpen (Wageningen University), to test this question in a systematic way.

With funding from the EU's Horizon 2020 Research and Innovation Programme, they collaborated with AiMark and GfK to build a unique data set combining their 10,000-household scanner panel data with survey data from a specially-made questionnaire.

Specifically, in a natural experiment spanning nine weeks, the panel households shopping at Albert Heijn (the largest supermarket retailer in the Netherlands), encountered eight perishable foods sold at regular price, at a straight discount, or on a multibuy.

Households then reported how these products were ultimately used, including whether any portion was thrown away.

Putting intuition to the test

The research particularly focused on these perishable items because they were basic household staples (like vegetables and bread) that are often wasted, and because they would need to be eaten or frozen within a reasonably short period (which simplified measurement).

Households that purchased under multibuys wasted less than households that purchased at regular prices

After matching samples to control for factors such as household size, income, and age, as well as declared attitudes to waste and frugality, the researchers concluded that discounted and multibuy purchases did not contribute to increased food wastage. In fact, households that purchased under multibuys wasted less than households that purchased at regular prices.

What did households in this experiment do with the extra food, now that we know they didn't let it spoil and throw it out? It seems they either ate more of it than usual, or they stored it. The researchers didn’t track the outcome of frozen food, but they pointed to research evidence that frozen food tends to be defrosted when needed and is rarely wasted.

For marketers trying to sell food in a responsible way, this is a crucial finding. It highlights that many intuitive ideas about why people buy and eat food might be wrong.

Diverse factors nudge shoppers toward one type of purchase over another: from seasonal price variations, expiration dates, or a preference for healthy choices. However, most of the previous research in this area was about how much people bought under different conditions – not what happened to the purchase afterwards.

Man in supermarket
The findings highlight that many intuitive ideas about why people buy and eat things might be wrong (Photo: Therese Petersson/Twenty20)

We have plenty of data on how promotions encourage people to buy, because this is what marketers are interested in.

But for anyone interested in health or environmental factors, this new research really matters. Public health targets require persuading people to buy healthier food, but it also requires ensuring that the food ends up on their plates, and not in a landfill.

Status: it's complicated

Above all, the research highlights the complexity of what motivates the choices made by supermarket shoppers.

This fieldwork took place in 2019, and so does not consider the impact of the coronavirus pandemic on consumer behaviours. However, it still reflects a wide range of factors that influence whether we buy more or less of something. Such factors include our anticipated consumption and our attitude towards value and good deals. These factors also include how we feel about the item itself; if something you and your family love is on special offer, you are more inclined to change your shopping plans and fill your trolley.

Impulse buys of mundane staples are much harder to inspire (in the absence of anticipated supply problems).

Food waste occurs as a consequence of a complex pattern of household behaviours

Consumers frequently buy everyday items with little thought, defaulting to what is familiar and accessible. In large supermarkets, where there might be more than 50 variants of a single product on offer, recognisable logos and brands combined with eye-level shelving play a huge role in determining the choices made by a busy shopper on "autopilot."

This makes the GfK panel used by the researchers, in which respondents scan the barcode of their actual purchases, the gold standard in tracking what people buy (compared with what they think /wish /would like people to think they bought).

Households, even within the parameters of a single supermarket chain’s customers, also vary hugely in price sensitivity. For some, a BOGOF deal may mean very little in terms of their overall food spending, whereas for others it takes a careful consideration of value and cash position to decide whether an unexpected bulk buy can be budgeted for at a given moment.

Larger households waste less in general, and are also keen consumers of multibuy offers, as one might expect.

Motivating better messaging

The implications for policymakers and marketers are complex. As the researchers conclude, "Food waste occurs as a consequence of a complex pattern of household behaviours, and we join others in advocating a more nuanced account of how and why it happens (or not)."

For marketers, better aligned messaging may be possible, along the lines of "buy one, freeze one," or better advice around storage and preservation. Such efforts could help reduce waste while still encouraging sales and engagement with promotional offers – and enable them to push back against lobbyists campaigning to limit deep discounting strategies.

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