(Bloomberg) -- Steve Ballmer passed Bill Gates on Monday to become the sixth-richest person in the world, the first time the former chief executive officer of Microsoft Corp. has been wealthier than the company’s co-founder. The move came as Microsoft shares rose to a fresh record, bringing their total gain this year to 21%. The company, through its partnership with OpenAI, has been one of the biggest beneficiaries of the artificial intelligence rally that has powered the US stock market higher. More than 90% of Ballmer’s $157.2 billion net worth is in Microsoft shares, according to the Bloomberg Billionaires Index.