Berkshire Hathaway has announced that its chairman, Warren E. Buffett, has converted Class A shares of his Berkshire holdings into Class B shares and donated almost all of the latter to five foundations.

According to the Omaha-based conglomerate, Buffett, a co-founder and signatory of the Giving Pledge, converted 11,867 of his Class A shares into more than 18.8 million Class B shares and donated nearly 17.7 million of the latter, valued at $3.4 billion, to the Bill & Melinda Gates Foundation and four foundations established by his late wife and children: the Susan Thompson Buffett Foundation, the Sherwood Foundation, the Howard G. Buffett Foundation, and the NoVo Foundation.

Since 2006 — when he pledged to gift 85 percent of his stake in Berkshire Hathaway to charity, Buffett has gifted about 43 percent of his Berkshire holdings, valued at about $31 billion, to the five foundations. Buffett intends to have all his Berkshire shares donated to charity through annual gifts that will be completed ten years after his estate is settled.