Unplanned Buying on Shopping Trips

David R. Bell, Daniel Corsten, and George Knox, 2010, 10-109

Motivated by the common wisdom that up to 70% of consumers’ purchases are decided upon in the store, marketers have expended considerable research energy on what in-store factors influence shoppers’ purchase decisions. But out-of-store factors influence unplanned purchases too, and if retailers understand those factors, they may be able to leverage them.

Here, David Bell, Daniel Corsten, and George Knox examine diary panel data from 441 households in a Western European country to uncover how several out-of-store factors influence unplanned purchases.

One major factor is the nature of the shopping goal: Is the consumer shopping to take advantage of a particular promotion or to buy a particular item—both concrete goals—or is the consumer shopping to take care of weekly needs, which is a more abstract goal? Reasons for choosing a particular store are also important. Did the shopper choose the store for its prices? Its selection? Its service? To avoid crowds? Convenience is a third factor: Is the consumer aiming to do one-stop shopping, or is he or she visiting a given store as part of a multiple-store shopping trip? The researchers also looked at the interaction between out-of-store and in-store advertising.

For each shopping trip participating households made during the two-week observation period, the shoppers recorded their reasons for the shopping trip and picked why they had chosen the stores they did from a list of possible reasons relating to the factors under investigation. They also completed a questionnaire in which they noted which of their purchases were planned and which were unplanned.

The researchers found that as shoppers’ overall shopping goals became more abstract, the shoppers made more unplanned purchases. Similarly, unplanned buying increased when shoppers chose a store for its low prices or its attractive promotions. A store’s assortment and service had no effect on unplanned purchases, however. When shoppers chose a store for the convenience of one-stop shopping, unplanned buying went up; when a store was one in a series of stores to be visited, by contrast, unplanned buying decreased. Finally, although out-of-store marketing had no significant direct effect on trip-level unplanned buying, there was an interaction between out-of-store marketing and in-store marketing that did boost unplanned buying.

These findings have immediate relevance for retailers. They show that ad campaigns such as Wal-Mart’s “Save Money. Live Better,” which focus on abstract shopping benefits, are likely to generate increased unplanned spending. In the current study, when shoppers’ goals were at their most abstract, their unplanned purchases went up 60%. Similarly, the fact that there is an interaction between out-of-store and in-store marketing that boosts unplanned spending suggests that retailers should reevaluate the importance of out-of-store advertising. The current study also validates focusing on the characteristics of the shopping trip rather than the shopper. That is, rather than focusing only on attracting particular types of customer, marketers and retailers may also fruitfully work on promoting a certain type of shopping trip (one with abstract goals, for example).

The research confirms that shopping trips to hard discounters, which offer low prices, a large selection, and the convenience of one-stop shopping, are more likely to have the most abstract goals (in the case of the two big-box discounters in the study, 53% and 44% of the visits were motivated by the most abstract goals). Interestingly, however, when shoppers visit supermarkets with an abstract goal in mind, there is an interaction between the supermarket format and the shopping goal that results in a boost in sales over and above what can be attributed to the abstract goal alone. The bottom line is that all retail formats benefit when the shoppers’ goals are abstract.

The current study was conducted in a single European country, and the researchers urge further research in other parts of the world to see how generalizable the results are and how well they apply to countries at other stages in the evolution of retail markets.

David R. Bell is Professor, Wharton School, University of Pennsylvania. Daniel Corsten is Professor, Instituto de Empresa Business School, Madrid. George Knox is Assistant Professor, Tilburg University, The Netherlands.


We thank Andre Bonfrer, Marnik Dekimpe, Els Gijsbrechts, Christophe Van den Bulte, seminar participants at the 2007 Wharton Marketing Conference, Ross Rizley, Susan Keane, and two anonymous MSI reviewers for their comments. We are very grateful to Sjoerd Schaafsma of Aecasis and Gilles Martin of Unilever for sharing knowledge and insights about shoppers and shopping, and for access to data, and also to Olga Liberzon of Deloitte Consulting LLP for valuable insights. Any errors, of course, are our own. Authorship is alphabetical; all authors contributed equally.

Related links

Can Out-of-store Marketing Boost Unplanned Buying? (2010) [Article]


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