We all have our own style when it comes to grocery shopping. Some of us bring a detailed shopping list and follow it to the letter. Others have a rough idea of what we need to buy, but are willing to consider other items if they’re on sale or simply look appealing. And some incorrigible impulse buyers simply arrive at the grocery store without any plan at all.
Of course, even the best-laid plans can be ruined by the prospect of a bag of gourmet popcorn or a sale on Starbucks Pumpkin Spice Frappuccinos.
To examine the behavior patterns of grocery shoppers over the course of a trip, Timothy Gilbride, Mendoza associate marketing professor and co-authors Jeffrey Inman of the University of Pittsburgh and Karen Melville Stilley of Market Rise Consulting recently set out to track a few shoppers as they completed their weekly grocery runs. Their paper, “The Role of Within-Trip Dynamics in Unplanned Versus Planned Purchase Behavior,” was published in the May 2015 edition of The Journal of Marketing.
“There had been other research that looked at the difference between the types of people who buy more unplanned stuff versus those who stuck to their list,” Gilbride said. “In this study, though, we wanted to look at a particular person and ask, does their purchasing pattern change within a trip?”
First, the researchers interviewed a group of shoppers about what they planned to buy on their trip, and how much they planned to spend. Then each shopper was given a barcode scanner and asked to scan each item as he or she put it into the cart. As the researchers expected, many shoppers ended up buying items that weren’t on their lists. Why? That’s where it gets complicated.
The researchers found that the longer shoppers stayed at the grocery store, the more likely they were to buy unplanned items. Within that general trend, though, shoppers tended to fall into two categories. People with smaller budgets who bought an unplanned item, say, a gallon of ice cream, tended to compensate by immediately buying a planned item, say, a package of diapers. This behavior is consistent with “self-regulation theory,” which hypothesizes that shoppers make buying decisions over the course of a trip with the overall goal of staying within their target budget.
On the other hand, the researchers found that people with larger budgets tended to follow up unplanned purchases with even more unplanned purchases. This behavior is more consistent with “cueing theory,” according to which seeing certain items they want to buy “cues” a shopper to remember other items they might have forgotten to put on their lists.
What are the implications of the study’s findings for shoppers? “Be mindful that the longer you shop, the more likely you are to make unplanned purchases,” Gilbride said. “We just get tired. What we know from psychology, though, is that if we can give ourselves a pep talk every now and again, and remind ourselves of our budget, then we can get back to our goals.”
In the near future, Gilbride said, grocery stores will have smartphone apps to allow shoppers to create shopping lists and then keep track of their purchases. Although that could help consumers stay within their budgets, it also could benefit retailers by allowing them to track their customers’ habits.
“So if I see that you bought an unplanned bag of pretzels,” Gilbride said, “I’d probably send you a message to say, ‘Did you also need chips or salsa, or whatever?’”
Gilbride said there’s nothing inherently bad about making unplanned purchases—in fact, shoppers seem to anticipate them. “Research has shown that if you ask people how much money they plan to spend in a shopping trip, they have one number, and then if you ask them to add up the prices of all the things they plan to buy, there’s a lower number. So there’s sort of a budget for unplanned items. The interesting thing is that people plan on making unplanned purchases.”