Correction: An earlier version of this article incorrectly said that Facebook CEO Mark Zuckerberg had increased the number of shares he planned to sell in the company’s public offering. This version has been corrected.

Facebook shareholders have increased the number of shares offered in the company’s public offering to just over 421 million. The company and its shareholders both also have upped the number of shares they will allow for over-allotment — shares set aside in case the offering doesn’t meet demand.

According to the company’s eighth amendment to its S-1, chief executive Mark Zuckerberg is not selling more of his shares, but will see his voting share power decrease slightly, to 55.8 percent from 57 percent.

Other shareholders who are selling additional shares include directors James Breyer and Peter Thiel, as well as Goldman Sachs and Tiger Global.

The company set its range for share prices at $34 to $38 per share and is expected to make its market debut Friday. With the additional shares in play, the company could raise as much as $16 billion in its initial public offering.

The social network is expected to set its final share pricing on Thursday, and begin trading Friday on the Nasdaq index under the ticker “FB.”

That would make Facebook’s offering, already expected to be the biggest for a technology company, the third-largest public offering in U.S. history, according to the research firm Renaissance Capital. If shareholders also sell the shares they’ve set aside for over-allotment, the offering could raise as much as $18 billion — which would edge out Visa’s top IPO of $17.8 billion.

(The Washington Post Co.'s chairman and chief executive, Donald E. Graham, is a member of Facebook's board of directors.)

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