CBS

For the first time in Microsoft's history, Bill Gates is no longer the company's largest individual shareholder, and in four years his ownership stake will likely vanish.

A stock sale by the software giant's former chief executive, revealed in a regulatory filing last week, reduced his holdings in the company to 330.1 million shares, putting him second behind fellow former CEO Steve Ballmer, who owns 333 millions shares, according to his most recent proxy statement. Ballmer retired in February with the announcement that Satya Nadella had been appointed the company's latest CEO.

The switch came when Gates, who founded the company in 1975 and served as its CEO until 2000, sold 4.6 million shares on April 30, according to a notice filed with the US Securities and Exchange Commission on Friday and first noticed by GeekWire. Each of the two men owns about 4 percent of the company's shares.

Gates has sold 80 million shares annually each of the past 12 years under a preset trading plan to fund the Bill & Melinda Gates Foundation. At the current rate, Gates will have no direct ownership stake of the company by mid-2018.

CNET has contacted Microsoft for comment and will update this report when we learn more.

Still the world's richest person with a fortune estimated at $76 billion, Gates has pledged to give away the bulk of his fortune to charity. He has already donated more than $28 billion to the Gates Foundation, which is working toward the eradication of polio, malaria, and other dangerous diseases.