Investor Warren Buffett has donated another $1.5 billion to the Bill & Melinda Gates Foundation, part of his plan that began in 2006 to donate 99 percent of his wealth.

According to a filing with the Securities and Exchange Commission, Buffett donated on Thursday 19.34 million Class B shares of his insurance and investment company Berkshire Hathaway Inc to the Gates Foundation.

The B shares closed up $1.25 at $77.77, while Berkshire Class A shares closed up $1,840 at $116,640.

Bill Gates, the co-founder of Microsoft Corp and a Berkshire director, and his wife Melinda created the Gates Foundation to address education, health and poverty problems.

Buffett, 80, annually donates smaller sums at about the same time of year to four family charities.

These include the Susan Thompson Buffett Foundation, named for Buffett's late first wife, and foundations for their children Howard, Peter and Susan.

Berkshire was not able to immediately provide further information about these donations, which are typically disclosed in SEC filings.

Buffett is the world's third-richest person, with a $50 billion net worth, Forbes magazine said in March.

The Gates Foundation said it employs 927 people, spent $2.6 billion last year, and has a $37.1 billion endowment.

Buffett expects the foundation to spend his gifts, which have totaled roughly $9.5 billion.

The number of shares that Buffett donates declines by 5 percent each year.

(Reporting by Jonathan Stempel; editing by Andre Grenon)

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