Amazon's ended trading Monday with a market value of about $797 billion, compared with Microsoft's $783 billion. Apple, which had been part of a close three-way race for the seat, is now down to about $702 billion in market value after plunging last week on the news of its weak iPhone sales. Google parent company Alphabet has surpassed Apple with a market value of about $748 billion.
Amazon's stock rose about 3.5 percent Monday to close at $1,629.51 per share, while Microsoft rose just a fraction of 1 percent to close at $102.06 per share. Microsoft announced Monday it was working with Kroger to take on Amazon's cashierless Amazon Go stores with its own take.