AIG: What's Driving Up the Stock?

Updated with closing stock price.

NEW YORK (TheStreet) -- AIG's (AIG Quote) massive run higher this week left much of Wall Street wondering what prompted it and where it will end.

AIG closed at $50.23 on Friday -- a 53% gain over last Friday's closing price of $32.85.

Shares of the New York-based insurer had alternated between positive and negative territory late Friday, but ultimately recovered. The stock continued rising in after-hours trading. It had earlier climbed as high as $55.90 and fallen as low as $45.55, in yet another day of heavy volume from small speculative bets.

On Thursday, volume hit more than 150 million, more than the 134 million shares outstanding, and six times more than the three-month average. But those shares being traded are held by a select few, including hedge funds that piled into financial names during the second quarter, switching from short positions held through the height of the financial crisis.

Taxpayers own about 80% of AIG, the troubled insurance giant, and their "fund manager" -- the Treasury Department -- is not in the trading game yet. The Treasury did not immediately respond to a request for comment, though it has indicated in the past that the government will not exit its positions in financial firms until they are more assuredly on safe ground. AIG, despite its stock surge, is most certainly not.

Even from an investment perspective, taxpayers selling AIG shares now would make little sense. The market value of public AIG holdings is $7.25 billion, just a tiny fraction of the $180 billion credit line the federal government has extended. In exchange, the Treasury received warrants to purchase millions of common shares.