Putting his money where his mouth is to the tune of $1 billion during the final week of January 2014, Carl Icahn bought $500 million of Apple Inc. (NASDAQ: AAPL) shares today despite December’s unfavorable earnings report.

At a moment when the technology giant’s unstoppable image may have been somewhat shaken by a morning plunge in stock prices, with the price of a share slipping by as much as 7.55% during the first hours of trading on February 28th, the billionaire investor’s robust optimism about its future potential may prove to be key to halting the decline of share prices and restoring investor confidence in the firm.

Just a few hours before the purchase, investment sites such as the Motley Fool were discussing the possibility that Mr. Icahn might regret backing Apple (AAPL) as strongly as he has, in light of the recent earnings developments. However, Mr. Icahn completed his massive purchase shortly after markets opened today, using Twitter to instantly announce his decision to the investing world. Declaring that he “just bought $500 mln more $AAPL shares,” he also noted his strong and continued support for Apple’s buyback program.

Mr. Icahn already held approximately $3.5 billion worth of Apple Inc.’s (AAPL) shares, according to Forbes magazine. A full one quarter of his current holdings of the company’s shares were acquired within the past seven days. His January 23 purchase, which matched today’s in size, was accompanied by a seven page open letter to his fellow investors. In this missive, he stated that Apple’s shares are actually seriously undervalued, pegging their true worth at close to 200 percent of current prices. This calculation was based on the Standard & Poor’s 500 price to earnings ratio.

The prominent Apple backer’s Tweet appeared to cause investors to sell off even more of the AAPL shares in their portfolios, at least initially, since company stock prices dipped immediately after his Twitter post. The investor remains sanguine, however, putting his faith in Apple’s history of success and the forward-looking product choices Tim Cook has slated for the coming year. In a followup statement to MSNBC, Mr. Icahn declared “The long-term picture is completely unchanged.

To me, it’s even more compelling for Apple to buy back stock now,” and appears to be prepared to take full advantage of the temporarily depressed prices following in the wake of yesterday’s earnings report.

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