Green, Yellow, Red: How Personalized Nutrition Feedback Shifts Grocery Purchases

We studied whether personalized nutritional feedback on past grocery purchases shifts subsequent consumer choices. In September 2020, Finland’s largest grocery retailer added a Nutrition Calculator to its digital purchase-history service. The calculator summarizes the nutritional profile of customers’ purchases, evaluates it against national nutrition recommendations, and presents feedback using green, yellow, and red indicators. Using retailer transaction data, we estimate a difference-in-differences event study. Our primary specification compares 9,743 consumers who had used the service for at least six months before the launch of the calculator with a matched control group that had not activated the service. The clearest effect is for sugar-intensive purchases, whose budget share falls by 0.25 percentage points on average and by up to 0.43 percentage points at the peak. The budget share of salt-intensive purchases also declines, although some of this movement predates the launch, making the evidence less conclusive. We found no systematic changes in the budget share of fat-intensive purchases. The effects are most pronounced among women and consumers under the age of 55.