In the past 12 months, Microsoft chairman Bill Gates has sold off 90 million shares, effectively reducing his holdings of Microsoft common stock by 13 per cent. He now holds roughly 591 million shares (of the 8.4 billion shares outstanding), and remains the company’s largest single stockholder. Gates’ rapid shedding of shares may set off alarm bells among investors, InformationWeek reports. Some critics would point to Windows Vista or the KIN phone as evidence that Microsoft is losing its grip. However, Microsoft officials have explained the selloff as smart investing—Gates is simply diversifying his holdings. And presumably, like most investors, Gates would like to see a decent return on his investment.