Microsoft chairman Bill Gates is continuing to sell shares in the company at a rate that might set off alarm bells for some investors. Regulatory documents filed Monday show that Gates sold 5 million shares on Feb. 3, and documents filed last Friday reveal that he sold an additional 5 million on Feb. 2.

The moves follow a year in which Gates aggressively pared back his Microsoft holdings. SEC records reviewed by InformationWeek show that, in the past 12 months, Gates has sold off a whopping 90 million shares—reducing his holdings of Microsoft common stock by 13%. Over the past two years, Gates has cut his interest in the company he co-founded by about 22% through more than a dozen separate transactions.

Gates now holds roughly 591 million Microsoft shares, or about 7% of the 8.4 billion shares outstanding, and remains its largest single stockholder.