The Globe and Mail reports in its Friday, Jan. 12, edition that Microsoft on Thursday briefly overtook Apple as the world's most valuable company for the first time since 2021 after the iPhone maker's shares made a weak start to the year. A Reuters dispatch to The Globe reports that Microsoft's shares have risen sharply since last year, thanks to the early lead the company has taken in generative artificial intelligence through an investment in ChatGPT-maker OpenAI. Microsoft's stock closed 0.5 per cent higher, giving it a market valuation of $2.85-trillion (all figures U.S.). It rose as much as 2 per cent during the session and the company was briefly worth $2.9-trillion. Shares of Apple closed 0.3 per cent lower, giving the company a market capitalization of $2.88-trillion. Microsoft and Apple have jostled for top spot over the years. "It was inevitable that Microsoft would overtake Apple since Microsoft is growing faster and has more to benefit from the generative AI revolution," said D.A. Davidson analyst Gil Luria. The weakness in Apple stock follows a series of rating downgrades that fanned worries that sales of the iPhone, its biggest cash cow, would stay weak, especially in major market China.