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On July 24, 2015, Amazon’s market cap surpassed Walmart’s. It took nearly 10 years for its revenue to do the same.

The once-scrappy online retailer had already expanded into cloud services and streaming video, but its revenue in that second quarter of 2015 was about one-fifth of Walmart’s, at $23.2 billion.

Yesterday, it posted fourth quarter sales of $187.8 billion, a 10% increase. Revenue from Walmart, whose numbers are due on Feb. 20, is predicted to rise 4% to $180 billion.

It was remarkable when Amazon reached the first milestone in 2015, a lesson for a young(er) reporter on the value investors put on prospects for growth. Besides being just a fraction of the size in revenue, Amazon had only just turned consistently profitable after a period of choppy gains and losses.

The company eclipsed Walmart in profit for the first time soon after that in 2017, and has frequently surpassed it since then — and significantly so in the past 18 months.

Of course, if Amazon was just a straight Walmart competitor, it wouldn’t have justified the stock’s climb. But it didn’t just make its profits selling stuff; it sold cloud storage and eventually added fancy produce, streaming, ad services, and now, most importantly, AI hopes to its portfolio. Hopes that continue to push Amazon’s trajectory far past the realms of the retail category the company completely reinvented by selling convenience as much as the goods themselves.

But just as you’d be foolish to pooh-pooh Google’s search or Microsoft's productivity segment (Office! Outlook!) for their flashier business segments, retail still demands respect as the biggest earner, still bigger than Amazon Web Services. While Amazon's cloud business now provides the AI buzz and the growth — sales rose 19% last quarter — it’s still dwarfed by the simple retail business of selling stuff. Online sales, which don’t include subsidiary Whole Foods or ad or third-party services, rose 7% to $75.6 billion.

What has all this meant for investors?

If you bought Amazon on the very day that the market cap lines crossed, you’d be up 802% compared to Walmart's 331%, which sits at a record close on Thursday. (Meanwhile, the S&P 500 gained 193%.)

Perhaps a fitting payoff for investors who bet on the growth story of a company that was once "famously unprofitable."

Julie Hyman is the co-host of Market Domination on Yahoo Finance. You can find her on social media @juleshyman.

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