Many U.S. shoppers who order grocery deliveries through Instacart are unknowingly part of widespread AI-enabled experiments that price identical products differently from one customer to the next—sometimes by as much as 23 percent. Instacart’s algorithmic pricing experiments were found to be occurring through the platform at several of the nation’s biggest grocery retailers, including Albertsons, Costco, Kroger, Safeway, Sprouts Farmers Market, and Target.

These are among the findings of a months-long investigation by Consumer Reports and Groundwork Collaborative, as part of a larger project with More Perfect Union, two nonprofit organizations with experience analyzing food prices. Via Consumer Reports:

Algorithmic pricing is usually invisible to consumers, who typically see only the prices and fees they’re offered. Researchers, meanwhile, are rarely granted access to the complex systems of algorithms, artificial intelligence, and data that parcel out individualized prices. CR’s investigation, which involved orchestrating simultaneous online shopping sessions with hundreds of volunteers, aimed to peek inside the black box.

Instacart has disclosed its pricing experiments in corporate marketing and investor materials, noting that “shoppers are not aware that they’re in an experiment.” But the company described the resulting price differences as small and “negligible.”

Our investigation suggests that the scope of Instacart’s price experiments—which are taking place against the backdrop of the fastest increase in food prices since the late 1970s—is far broader and more costly to some consumers than has been publicly acknowledged. Every one of the volunteer shoppers who participated in our tests was subject to algorithmic price experiments.