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Grocery Shopping PsychologyAn Anchoring and Adjustment Model of Purchase Quantity DecisionsStudies in 87 grocery stores show that signs with numbers in them (Limit 12 per/person; 3 for $3.00; Buy 6 for the weekend) can unknowingly double how many you buy. AbstractHow do consumers decide how many units to buy? This is a key issue for researchers, retailers, and manufacturers. While past research has focused on purchase incidence and brand choice, this research focuses on the psychological process behind the purchase quantity decision and shows how marketers can exert influence. We propose that a simple anchoring and adjustment judgment model describes how consumers make purchase quantity decisions. This process also suggests ways in which simple point-of-purchase (POP) materials can be employed to affect the quantity decision. Two field experiments and three lab studies show that external anchors have a powerful impact on quantity decisions whether presented in the form of multiple unit prices, purchase quantity limits, suggestive selling anchors, or even irrelevant anchors. A final study provides more direct evidence of the underlying judgment process and shows that people can be encouraged to retrieve alternative internal anchors that either expand or contract purchase intentions, eliminating the external anchor effect. SummaryBuying More: Why Numerical Signs Make You Overspend at the Grocery Store Numerical signs, such as “2 for $2” or “Limit 12 per person” make you spend twice as much as you planned. Studies conducted by researchers at the Food and Brand Lab found that certain promotions have great effect on the number of goods purchased. The four studies spanned 89 supermarkets and thousands of consumers. The findings were published in the Journal of Marketing Research* . The research indicates that promotions that utilized multi-unit pricing (“3 for $3”), purchase limits (“Limit 12/person”) and suggestive selling (“Buy 10 for your freezer”) all doubled the amount consumers purchased – and such promotions can be found throughout grocery stores across the country. When most people buy products, they buy one or two at a time. They decide on a low number (like one or two), then buy more if the product’s on sale. When promotions suggest high numbers (“Buy 12 so you don’t run out!”), people shift their reference point to the higher number, and buy more. “All three types of promotions increase purchase amounts from 30% to 105% of what the consumer would normally plan on buying,” said Dr. Brian Wansink, director of the Cornell Food and Brand. “But, consumers can counteract these promotions. They can write their purchase amounts on their shopping lists and stick to it.” Wansink said that consumers should always be aware of what is really being offered and he offered some “words of wisdom” to consumers. • Be aware of what the advertisements and deals really mean for you, know how much you’re actually saving and remember that smaller numbers don’t always mean a better deal – but neither do the big numbers. • Lower limits (two per visit) make consumers buy the product more often while high limits (12 per person) increase the amount of the sale for that visit. • Suggestive selling (Grab six for studying) is not a sale. They’re just promoting the product. Wansink said the more aware consumers are, the less likely they are to find themselves with a cabinet full of unneeded and unwanted products. For more information see Wansink, Brian, Robert J. Kent, and Stephen J. Hoch (1998), “An Anchoring and Adjustment Model of Purchase Quantity Decisions,” Journal of Marketing Research, 35:1 (February), 71-81. Reprinted with permission from Journal of Marketing Research, published by the American Marketing Association www.marketingpower.com/content1054.php. Contact: * These studies were conducted at the University of Illinois, former location of the Cornell Food and Brand Lab.
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