Why Impulse Buys Happen Without a List
Shoppers who arrive without a clear goal are far more likely to buy something unplanned, and hunger explains surprisingly little of it. The famous 62 per cent impulse figure turns out to be background, not a finding.
Key takeaways
- In a 2026 receipt study of 323 shoppers led by Sait Durgun, browsers had nearly nine times the odds of an unplanned purchase compared with shoppers on a routine trip.
- Hunger showed no reliable link with unplanned buying across the whole basket in that 2026 study, only in snacks and confectionery.
- Inman, Winer and Ferraro's 2009 study of 2,300 shoppers put the baseline chance of an unplanned purchase at 46 per cent, rising to as much as 93 per cent.
- The widely quoted 62 per cent impulse figure appears as background in a 2020 meta-analysis, which credits it to a 2015 newspaper column.
- Block and Morwitz found in 1999 that shopping lists held only about 40 per cent of what shoppers went on to buy.
Why does a shopper who wanders into a supermarket with no errand in mind leave with more than one who came for milk and bread? The obvious answer is weak willpower, or an empty stomach, and both are part of the folklore of impulse buying. A recent receipt study points somewhere else. Its authors coded thousands of items bought by a few hundred shoppers and found that the reason for the trip predicted unplanned purchases far better than hunger did. So what actually decides how much of a basket was never meant to be there, and can a list change it?
What the receipts showed about browsing
The study, led by Sait Durgun and published in the Journal of Retailing and Consumer Services, recorded how hungry shoppers were and why they had come, then went through their receipts item by item, sorting planned purchases from unplanned ones. Across the whole basket, hunger showed no reliable link with unplanned buying. The trip's purpose was the clearest predictor the study reported. Shoppers who said they were browsing had nearly nine times the odds of an unplanned purchase compared with shoppers on a routine trip.
Hunger did matter in one aisle. In snacks and confectionery, hungrier shoppers bought more that they had not planned, and the effect survived the corrections researchers apply when they run many tests at once. Separately, hunger predicted unplanned buying among younger shoppers more than older ones. The old advice about not shopping hungry survives, but as a warning about the biscuit shelf rather than the whole trolley.
The study observed shoppers rather than assigning them to browse, so browsers may differ from routine shoppers in ways the receipts cannot show. An older study gets round part of that problem. David Bell, Daniel Corsten and George Knox, writing in the Journal of Marketing in 2011, used panel data that followed the same households across many trips, which lets a researcher compare a shopper with herself. They found that unplanned buying rose steadily with how abstract the goal for the trip was before the shopper left home. A vague goal produced more unplanned buying than a specific one, in the same people.
The same paper found two further patterns. Unplanned buying was higher on trips where the shopper picked the store for its prices, and lower when the store was one stop on a trip to several. One reading is that a shopper who has come for bargains keeps looking for them, while a shopper with other shops still to visit has less time to wander.
How much of a basket is never planned
The best-known figure in this field is large. The Future of Shopping, the 2022 retail forecast by Jörg Snoeck and Pauline Neerman, states in its chapter on the future of the store that as many as 62 per cent of in-store purchases are impulse purchases, and credits the figure to Iyer and colleagues. Our review of the book rated that line as its single best-sourced statistic, because it points to a peer-reviewed meta-analysis rather than a vendor survey.
The meta-analysis is real and substantial. Gopalkrishnan Iyer and three colleagues pooled 231 samples and more than 75,000 consumers in the Journal of the Academy of Marketing Science, published online in 2019 and in print in 2020. Read in full, though, it does not produce the 62 per cent. The figure appears once, in the introduction, as an estimate, and the paper credits it to a 2015 newspaper column on the psychology of impulsive shopping. The book cites the right paper for the number, but the paper had taken it from a newspaper column.
The book cites the right paper for the number; the paper had borrowed it from somewhere lighter.
Researchers also measure two different things under one heading. Unplanned buying compares what a shopper says she intends to buy with what ends up on the receipt. Impulse buying, in a widely used definition, from a 1987 paper by D. W. Rook, is stricter: an episode in which "a consumer experiences a sudden, often powerful and persistent urge to buy something immediately". Plenty of unplanned purchases involve no urge at all, such as remembering the washing-up liquid at the shelf.
The best-known field estimate of unplanned buying comes from J. Jeffrey Inman, Russell Winer and Rosellina Ferraro, who interviewed 2,300 shoppers in 28 stores for a 2009 paper in the Journal of Marketing. The figures that tend to get quoted sit side by side below.
| Source | What was measured | Figure |
|---|---|---|
| Inman, Winer and Ferraro, 2009 | Baseline chance that a purchase was unplanned | 46 per cent |
| Inman, Winer and Ferraro, 2009 | The same chance with contextual factors stacked up | up to 93 per cent |
| Block and Morwitz, 1999 | Share of items bought that had been written on the list | about 40 per cent |
| Block and Morwitz, 1999 | Share of listed items that were bought | more than 80 per cent |
| Iyer and colleagues, 2020 | In-store purchases made on impulse, quoted as background | as many as 62 per cent |
Read together, the rows say something more useful than any single headline. Much of what goes into a basket was not on a list, and the share swings widely with circumstances. How much of that is impulse in the strict sense, a felt urge rather than a remembered need, is a separate question, and none of these figures answers it.
Willpower, or the shape of the trip
One account of impulse buying puts the cause inside the shopper. Kathleen Vohs and Ronald Faber, in the Journal of Consumer Research in 2007, ran three studies in which some participants first did a task meant to tire their self-control. Those participants felt stronger urges to buy, said they would pay more, and actually spent more money when an unexpected chance to buy came up. On this view, the supermarket at the end of a long day catches people when their capacity to resist has run down, an idea known as ego depletion.
The idea has had a hard decade. A registered replication led by Martin Hagger in 2016, run across 23 laboratories with 2,141 participants, found an effect too small to tell apart from zero. Vohs herself then led a preregistered test across 36 laboratories and 3,531 participants, published in 2021, and its planned analyses found no evidence for the effect.
The Iyer meta-analysis does link higher self-control to fewer impulse purchases, but that mostly compares people who differ in a trait. It does not show that a tiring day drains a tank. The same meta-analysis counted marketing stimuli, such as price discounts, promotions and store atmosphere, among the main triggers of an impulse purchase, alongside the shopper's motives, which already points outside the shopper's reserves.
The second account puts the cause in the structure of the trip. A specific goal, set before entering the store, gives each shelf a simple test: is this what I came for? A vague goal gives every shelf a chance. That account fits the Durgun receipts and the Bell panel, two different methods, and the Inman store interviews are consistent with it.
We think the trip explains more than the shopper's reserves do. The depletion account rests on laboratory tasks that have not held up when repeated at scale, while the trip-goal account has support from receipts, household panels and store interviews. Self-control as a stable trait may still play a part, though these studies do not measure it.
We think the trip explains more than the shopper's reserves do.
Making a shopping list that holds
The evidence on lists is encouraging and incomplete. Inman's team found that list use was one of several habits linked to fewer unplanned purchases, alongside more frequent trips, visiting fewer aisles, spending less time in the store and paying by cash. Lauren Block and Vicki Morwitz, analysing the real lists and purchases of a panel of shoppers over two months in 1999, found that more than 80 per cent of listed items were bought. The list did its job as a memory aid. It also held only about 40 per cent of what people ended up buying.
A list can carry its own escape hatch. Karen Stilley, Inman and Kirk Wakefield reported in 2010 that many shoppers walk in with a mental budget that includes an unassigned amount, in-store slack, kept for whatever they decide on at the shelf. A list with no total leaves that slack open.
The practical version follows from the studies, though nobody has tested the whole package as one routine. Write the goal of the trip in specific words before leaving, the meal or the gap in the cupboard. Put a number on the slack you are willing to spend. Shop with a purpose for each trip and through fewer aisles, and if you arrive hungry, skip the snack aisle. Browsing is a hobby, and it should be budgeted like one.
Common questions
What share of supermarket purchases are unplanned?
In a 2009 study of 2,300 shoppers in 28 stores, J. Jeffrey Inman and colleagues put the baseline chance that a purchase was unplanned at 46 per cent, rising to as much as 93 per cent when contextual factors combined. The often-quoted 62 per cent impulse figure is background in a 2020 meta-analysis, not one of its results.
Does shopping hungry make you buy more?
Not across the whole basket, according to a 2026 receipt study of 323 shoppers led by Sait Durgun. Hunger mattered for snacks and confectionery, and for younger shoppers. The purpose of the trip was a far stronger predictor, with browsers showing nearly nine times the odds of an unplanned purchase.
Do shopping lists stop impulse buying?
They help. Inman's 2009 study linked list use to fewer unplanned purchases, and Block and Morwitz found in 1999 that more than 80 per cent of listed items were bought. But lists held only about 40 per cent of what shoppers bought, and many shoppers leave room in their budget for unplanned buys.
Sources
Durgun, S., Çetinkaya, B. D., & Koç, H. (2026). “Don’t shop hungry? A receipt-based field study of hunger, shopping purpose, and unplanned purchasing.” Journal of Retailing and Consumer Services, 93, 104947. doi:10.1016/j.jretconser.2026.104947. Abstract read: 323 shoppers, 3,819 coded items; hunger and basket-level unplanned purchasing OR 1.019, p = .434; snacks and confectionery OR 1.090, p = .001, survives Bonferroni and FDR; shopping purpose eta squared .223; browsing against routine OR 8.635; hunger by age interaction p = .014.
Bell, D., Corsten, D., & Knox, G. (2011). “From point of purchase to path to purchase: how preshopping factors drive unplanned buying.” Journal of Marketing, 75(1), 31-45. doi:10.1509/jmkg.75.1.31. Abstract read: panel data holding the shopper constant; unplanned buying increases monotonically with the abstractness of the trip goal; higher when the store is chosen for pricing, lower on multistore trips.
Inman, J. J., Winer, R. S., & Ferraro, R. (2009). “The interplay among category characteristics, customer characteristics, and customer activities on in-store decision making.” Journal of Marketing, 73(5), 19-29. doi:10.1509/jmkg.73.5.19. Abstract read: 2,300 consumers, 28 stores; baseline probability of an unplanned purchase 46 per cent, up to 93 per cent; list use, more frequent trips, fewer aisles, less time in store and paying by cash reduce unplanned purchasing. The 2004 working-paper version was also read in full.
Iyer, G. R., Blut, M., Xiao, S. H., & Grewal, D. (2020). “Impulse buying: a meta-analytic review.” Journal of the Academy of Marketing Science, 48, 384-404. Published online 9 July 2019. doi:10.1007/s11747-019-00670-w. Full text read: 231 samples, more than 75,000 consumers; the 62 per cent figure appears in the introduction as an estimate credited to Chamorro-Premuzic, T. (2015), 'The psychology of impulsive shopping', The Guardian, 26 November; Rook's 1987 definition quoted at p. 384; self-control reduces the likelihood of impulse purchases in the structural model.
Vohs, K. D., & Faber, R. J. (2007). “Spent resources: self-regulatory resource availability affects impulse buying.” Journal of Consumer Research, 33(4), 537-547. doi:10.1086/510228. Abstract read: three investigations; depleted participants felt stronger urges to buy, were willing to spend more and spent more.
Hagger, M. S., Chatzisarantis, N. L. D., Alberts, H., et al. (2016). “A multilab preregistered replication of the ego-depletion effect.” Perspectives on Psychological Science, 11(4), 546–573. 23 labs, N = 2,141, d = 0.04, 95% CI [−0.07, 0.15].
Vohs, K. D., Schmeichel, B. J., Lohmann, S., et al. (2021). “A multisite preregistered paradigmatic test of the ego-depletion effect.” Psychological Science, 32(10), 1566–1581. 36 labs, N = 3,531, d = 0.06.
Block, L., & Morwitz, V. G. (1999). “Shopping lists as an external memory aid for grocery shopping: influences on list writing and list fulfillment.” Journal of Consumer Psychology, 8(4), 343-375. doi:10.1207/s15327663jcp0804_01. Abstract read: panel over two months; lists record about 40 per cent of items ultimately bought; more than 80 per cent of listed items bought.
Stilley, K. M., Inman, J. J., & Wakefield, K. L. (2010). “Planning to make unplanned purchases? The role of in-store slack in budget deviation.” Journal of Consumer Research, 37(2), 264-278. doi:10.1086/651567. Abstract read: mental trip budgets contain an itemised portion and in-store slack; incidence of slack found in a secondary data set and a field study.
Rook, D. W. (1987). “The buying impulse.” Journal of Consumer Research, 14(2), 189-199. Definition read as quoted verbatim in Iyer et al. (2020), p. 384; the original was not opened.
Snoeck, J., & Neerman, P. (2022). The Future of Shopping: Re-set Re-made Re-tail. LannooCampus. Read in full by this publication, with a reliability audit. Ch. 4, The Future of the Store, IMG_4665 (pp.108 to 109): the 62 per cent impulse-purchase figure credited to Iyer et al. (2019).