The Day a Tweet from Carl Icahn Raised Apple's Value by $20 Billion [Update]

Then there was the day that a couple of tweets from Carl Icahn sent Apple Inc.'s stock up almost 5 percent. That day was Tuesday, when shares of $AAPL rose US$22.21 (+4.75 percent) to close at $489.57, and it did so on three times the average volume with 31.3 million shares trading hands.

Carl Icahn is a fabulously successful rabble rouser famous for the "Icahn Lift" and infamous for both aggressive corporate raiding and shareholder activism. On Tuesday, Mr. Icahn supplied that Icahn Lift to Apple by announcing—via Twitter—that he has taken a "large position" in the company.

His tweet:

That was followed immediately by a second tweet, where he said that he had spoken with Apple CEO Tim Cook (you can do that when you're Carl Icahn):

Bloomberg reported that Mr. Icahn's stake is more than $1 billion—if you're keeping score at home, that's a lot of money. He accumulated that position over the last month, before he made his announcement. He also told Bloomberg that he believes Apple's proper value is more like $600 per share.

The markets reacted almost immediately, as you can see in the chart below. That sharp jump in the early afternoon session coincided with Mr. Icahn's tweets, which went out at 2:25 PM EDT.

AAPL Chart

$AAPL Chart for August 13th, 2013
Source: Yahoo! Finance

And that, kids, is how one man's opinions can undo the concerted work of Apple's doubters with a few strokes of his keyboard or taps of his fingers. It's kind of like Doug Kass, but rather than being based on nothing and fleeting as a fat man's gas, the Icahn Lift tends to have a lasting impact on a company's stock performance.

Mr. Icahn's most recent shareholder battles has been in Dell's board room, where Mr. Icahn has fought (unsuccessfully, so far) to scuttle Michael Dell's efforts to take his namesake company private.

Mr. Icahn has argued that the deal offered by Mr. Dell and his backers short changes Dell's investors, and he pushed for a separate buyout offer by a rival group of investors. He is currently suing Dell to block the sale.

It's a rare failure for Mr. Icahn, but he has history of betting big—think go big or go home. It will be interesting to see what comes out of his newfound interest in Apple.

[Updated with more information on Mr. Icahn's stake. - Editor]

*In the interest of full disclosure, the author holds a tiny, almost insignificant share in AAPL stock that was not an influence in the creation of this article.