When Amazon (NASDAQ: AMZN) acquired Whole Foods in 2017, many analysts predicted that the e-commerce giant would disrupt traditional supermarkets. Amazon's total grocery sales rose 45% last year, according to research firm Edge by Ascential, with digital sales increasing 12.5% to $8.2 billion. Data: Edge by Ascential. Chart by author. That represents just 3.5% of Amazon's 2018 revenue, but it still led the market. However, Walmart (NYSE: WMT) and Kroger (NYSE: KR) -- which posted 10.1% and 66% digital grocery sales growth in 2018, respectively -- could still close the gap. Edge attributed Amazon's growth to robust sales of nonperishable groceries like cold beverages, coffee, snacks, and breakfast foods, but noted that sales of fresh fruit, vegetables, and meat remained soft. Amazon is trying to sell more perishable foods with Prime Pantry, Amazon Fresh, and Whole Foods delivery options, but these plans face fierce competition from new curbside pickup and delivery options at Walmart and Kroger. Business Insider Intelligence recently claimed that instead of disrupting the online grocery market, "the threat of Amazon led to competing grocers taking e-commerce seriously and becoming stronger competitors online." Simply put, Amazon leads the market now, but it's far too early to declare it the victor. Offer from The Motley Fool: The 10 best stocks to buy nowMotley Fool co-founders Tom and David Gardner have spent more than a decade beating the market. In fact, the newsletter they run, Motley Fool Stock Advisor, has quadrupled the S&P 500!* Tom and David just revealed their ten top stock picks for investors to buy right now. Click here to get access to the full list! *Stock Advisor returns as of June 1, 2019.John Mackey, CEO of Whole Foods Market, an Amazon subsidiary, is a member of The Motley Fool's board of directors. Leo Sun owns shares of Amazon. The Motley Fool owns shares of and recommends Amazon. The Motley Fool has a disclosure policy.Source