Harvard Study Finds Consumers Using Re-Usable Grocery Shopping Bags Purchase Marginally More Junk Food

Consumers bringing their own re-usable grocery bags tend to buy themselves more junk food, a working paper by the Harvard Business School has revealed. Researchers found that consumers subconsciously perceive bringing re-usable grocery bags as a positive initiative, and tend to reward themselves for this by purchasing more junk food.

The study is based on data collated from loyalty cards over a period of two years at a grocery-store chain in California. The data was analyzed by researchers Bryan Bollinger and Uma R. Karmarkar, who sifted through about 1 million transactions. The store, where the data was collected from, offered a discount to customers who brought in re-usable grocery bags. The small discount amount was marked on the receipt issued at the tills – this allowed researchers to differentiate between those customers who were bringing in their own bags and those who weren’t. 

The researchers, for the purpose of this study, did not include certain types of transactions, such as: Late-night store visits or the purchase of just one or two items. This was done to weed out atypical shopping behavior. An analysis of the data revealed that a small percentage of these consumers – 0.25% -- were more inclined to buy basic foods (eggs and milk) with organic labels. However, these consumers were also noticed to have a slightly higher inclination – 1.24% – were more inclined to junk food (nonorganic) items such as chips and candy.

While the researchers acknowledge that these numbers are not significant, Karmarkar said that the results could likely have been slightly different if they had also gathered data from an additional location, such as the East Coast.