Kroger customers have shifted more than $12 billion in CPG spending to Amazon, Walmart and Costco over the past year, according to data released Thursday by Numerator, with Kroger directly losing more than $1 billion from those shifts.

The figures expose pressure building beneath Kroger's turnaround efforts. The retailer has maintained its overall shopper base, Numerator reported, but the composition of that base is changing: Kroger added more than 1 million high-income households over the past year while losing 700,000 lower-income households. Lower-income shoppers who stayed also spent less.

The spending erosion comes as Kroger invests in price to drive traffic, making the competitive pressure harder to absorb.

Performance is uneven across Kroger's banner portfolio. CPG spending at stores branded Kroger fell $715 million year over year, with shoppers making 9 million fewer trips. Ralphs lost $516 million in CPG spending on 5.5 million fewer trips. Fry's Food Stores moved in the opposite direction, growing $365 million on 8.5 million additional trips.

Low-income households account for a $1 billion spending gap at Kroger. These shoppers cut CPG spending at the retailer by 5.2% year over year, driven by 30 million fewer trips. Numerator noted these households pulled back slightly less at Kroger than they did at Walmart.

Category-level data shows shoppers concentrating spending on grocery staples. Beverages, candy and canned goods drove $800 million in growth over the past year. Household items—laundry, dishwashing, cleaners and paper products—declined $97 million. Health and beauty products fell $178 million.

Kroger's fresh private label offers one clear growth pocket. The retailer's owned brands across produce, meat, deli and prepared foods, seafood and in-store bakery grew $420 million in the past year, Numerator found.

The combination of competitive spending shifts and weakness outside grocery means Kroger's price investments will need to accelerate traffic gains—and its fresh private label momentum—if the retailer wants to close a gap that wider rivals keep widening.