Fewer competing grocery stores means Walmart has an enormous amount of power to dictate what foods are available in these communities, shaping what people eat but also what food is produced, how, and by whom. It also means communities may be paying more for groceries in the long run, as several lawsuits have alleged that Walmart increased prices once it was the only game in town.

Walmart’s growing size also gives the chain incredible buyer power to hoard more of the food dollar at the expense of workers and producers. In 1990, when Walmart barely sold any groceries, ranchers received nearly 60 cents of every dollar spent on beef, while retailers received 33 cents. By 2009, Walmart had come to sell 23 percent of groceries, and ranchers’ share of the beef dollar shrunk to 42 cents while retailers’ share grew to 49 cents.

Workers wages also take a hit when supplying companies have fewer buyers. A study by Nathan Wilmers found that companies that primarily sell to one or two large buyers paid their workers less over time, as these dominant buyers can demand lower and lower prices.

Despite Walmart’s historic market share and economic harms, Congress and federal antitrust agencies have not stepped up to curb the chain’s power.

As Mitchell notes, Walmart is not the first grocery chain to squeeze suppliers or sell goods at a loss. In the 1920s, dominant supermarket A&P used a similar playbook to claim 16 percent of U.S. grocery sales. Lawmakers attempted to check the chain’s power with the Robinson-Patman Act, which prohibited stores from selling goods below-cost in one location and at a premium in another. It also required sellers to offer the same price to all buyers, regardless of size.

Under this statute, the Federal Trade Commission successfully sued the chain on two separate accounts, though A&P remained dominant into the 1950s, before losing steam in the shift to suburban supermarkets.

In recent years, the Justice Department and Federal Trade Commission have shelved the Robinson-Patman Act because it does not fit into current antitrust doctrine, which prioritizes low consumer prices above all other outcomes. “We have a law on the books that isn’t enforced,” says Mitchell. “We have agencies that have made a policy decision and they need to be held accountable for that.”

Supreme Court rulings have also made it very difficult to prosecute predatory pricing by large, well-capitalized corporations, making it far easier for dominant sellers like Walmart to undercut their competitors. Mitchell argues that policymakers and federal agencies need to crack down on these anticompetitive tactics that create an unequal playing field for smaller businesses.

“Our policy now as it’s been carried out for the last 40 years favors the big guys solely because they’re large and have financial resources, not because they’re better competitors, and I think that’s the fundamental issue,” Mitchell says.

This article originally appeared in Food and Power, and is reprinted with permission.