The study also lauded Walmart for helping small-scale farmers buy their own land, offering better contracts to cooperatives selling commodities, working with women’s rights organizations, and sourcing more from women and Fairtrade producers.

The one area where Whole Foods bested America’s largest grocery store? More loans for local producers, according to the scorecard.

“It is surprising that Walmart, for many, came out ahead of Whole Foods, because obviously Whole Foods does promote itself as a sustainable grocer,” says Oxfam’s Irit Tamir, who runs advocacy campaigns that target the private sector. “But we weren’t looking at environmental policies.”

The scorecard is included in a trio of new studies released by Oxfam that look at how supermarkets influence the treatment of international farmers and workers that form the backbone of the global food system. The charity studied how a dozen commodities, including coffee, tea, cocoa, orange juice, bananas, grapes, avocados and green beans, end up on shelves.

On average, the workers in those supply chains are well below a livable wage—and wages have gotten worse since the ‘90s.

“If you look at those commodities, the share of the value that supermarkets are taking, versus what producers and workers are getting in the supply chain, has increased over time,” says Tamir. “Where it was about 10 percent back in the nineties, it’s now about five percent, on average, that small-scale farmers are getting.”

Among the commodities Oxfam studied, a few products in particular illustrate how much that disparity has worsened. Indian workers in the tea industry make only 38 percent of what would be considered a living wage. Similarly, Kenyan green bean farmers only make 53 percent of a living income, while small-scale coffee farmers in Columbia earn 71 percent.

Shrimp processed in Southeast Asia, too, is illustrative of the growing inequality between supermarket chains and their downstream workers. In Indonesia, women peeling shrimp earn less than two euro cents for every pack sold at Albert Heijn, a Dutch supermarket owned by Ahold Delhaize, for five euros.

Why the disparity? Because supermarkets are capturing more and more of the value of that shrimp. Between 2000 and 2015, as the average consumer price of shrimp has gone up, so too has American, British, German and Dutch supermarkets’ share of the profit, rising by 66 percent, the study finds.