Amazon remains a small player in the $800 billion US grocery business, which is dominated by mega-chains like Walmart, Kroger, Costco and Albertsons. The new customers migrating to Whole Foods from Walmart make up less than 1% of Walmart's customer base, Thasos noted. It is also unclear if Walmart customers are defecting permanently or are temporarily curious about Whole Foods following a spate of media coverage.