The world’s largest online retailer could grow almost a third bigger in the next four years.

Amazon.com Inc. (AMZN.O) is on track to reach US$1 trillion in market capitalization by 2022, according to a sum-of-the-parts analysis from Jefferies analyst Brent Thill. That would be a 29 per cent jump from Monday’s valuation of US$773.8 billion, already greater than the combined market value of Walmart Inc. (WMT.N) and Alibaba Group Holding Ltd (BABA.N), the next two biggest retailers.

Thill sees “plenty of avenues” for Amazon’s revenue to more than double over four years to near US$500 billion. The company’s aggressive push to expand its advertising business will be a key driver, as the shift in ad spending to online platforms has helped it grow without needing to compete for dollars with Facebook Inc. or Alphabet Inc.’s (GOOGL.O) Google. And having “billions of touch points with consumers” helps Amazon distinguish itself from other ad markets, putting it on the path to reach US$22 billion in ad revenue by 2022, Thill says, up from about US$4 billion last year.

Thill rates the stock a buy and raised his 12-month price target to US$1,850 from US$1,750, compared with the average target of US$1,701, according to data compiled by Bloomberg. Still, Amazon could reach US$1 trillion sooner than even Thill expects. Analysts from Wolfe Research and Monness, Crespi, Hardt & Co. both carry price targets of US$2,000, which would put Amazon just shy of the trillion-dollar mark within a year based on the current number of shares outstanding.