Consumers spent $610 billion on Amazon between June 2020 and June 2021, while Wal-Mart said it only spent $566 billion. Analysts have long predicted that Amazon's sales would eventually surpass Wal-Mart's. Walmart's U.S. sales are still better than Amazon's, but the New York Times, citing JPMorgan's estimates, notes that it will reverse in 2022. Amazon's sales trend appears to be accelerating as the pandemic encourages people to switch to online shopping.

Neither Amazon nor Walmart responded to requests for comment.

Amazon has been trying to make itself look smaller. Founder Jeff Bezos testified to The US Congress in 2020 that Walmart was twice the size of Amazon. Amazon's role in the retail ecosystem is small, accounting for "just 4% of U.S. retail sales," Insider previously reported.

Seattle-based Amazon may be more vulnerable to antitrust law than ever after it overtook Wal-Mart in sales. Karl Racine, the US attorney in Washington, DC, is now suing Amazon, claiming it is the exclusive company that controls the prices of goods online. In 2017, the new head of the Federal Trade Commission, Lina Kahn, wrote a paper arguing that antitrust laws were outdated and incompatible with Amazon.

Despite all the antitrust storms, Amazon's growth hasn't slowed. Faisal Masud, chief executive of Fabric, an e-commerce startup, worked for Amazon during its "weak growth years" from 2002 to 2011. He says Amazon's rapid growth is due to its strength in third-party sales, its subscription model, Amazon Prime, and its last-mile logistics capabilities.