What’s Amazon’s Share of Retail? Depends Who You Ask

Critics who believe Amazon has gotten too big and powerful often quote estimates that the company accounts for nearly 50% of online sales in the U.S. But one widely cited source for that figure—the research firm eMarketer—recently revised Amazon’s market share estimate sharply downward after the ecommerce giant disclosed new data.

A spokesperson for eMarketer told The Information that the firm lowered its 2019 estimate for Amazon’s share of U.S. online sales to 37.7% after getting “new guidance” from data in Amazon CEO Jeff Bezos' shareholder letter. The revision, which hasn’t been previously reported, comes as Congress launches hearings into the market power of big tech companies and regulators are preparing possible antitrust probes of them. Estimates of Amazon’s market share are likely to be critical in any antitrust review of the company.