Market cap is an expression of how much investors think a company's stock is worth. For an apples-to-apples comparison of real growth, you want to compare _rev

Market cap is an expression of how much investors think a company's stock is worth. For an apples-to-apples comparison of real growth, you want to compare _revenue_, not market cap. Amazon has not yet passed Walmart in retail revenue (as of 2020) though it's true their revenue is growing much faster. Hence the XKCD references.