The reserves of American International Group’s property-casualty businesses may be short by about $11.9 billion, according to a new independent analysis.

The assessment, outlined in a report provided to clients of New York investment research firm Sanford C. Bernstein Nov. 30, would contrast the general assessment of AIG’s property-casualty businesses since its initial federal bailout in September 2008.

At the time, regulators said the fiscal soundness and value of the property-casualty operations – as opposed to its troubled derivatives portfolio maintained by AIG’s Financial Products division – would ultimately enable the troubled global insurance and financial services firm to pay its debt to the government. The company would receive nearly $180 billion in U.S. recovery funds over the next year, and still owes about $120 billion to taxpayers.

Its property-casualty operations were renamed Chartis last year, as AIG began selling off some of its operations to focus more heavily on its property-casualty core.

The Bernstein report’s distribution, reported in the New York Times, caused the company’s stock to fall 15% later that day, as AIG officials declined comment. Over the last year, several prior reports had indicated problems with AIG’s property-casualty reserves, which company officials denied.

In September 2007, Pennsylvania, Insurance Commissioner Joel Ario tried to reassure taxpayers as the government offered the troubled global company nearly $85 billion in initial bailout funds. Speaking on CNBC, Ario was the first to publicly suggest that the “gold bars,” AIG’s property-casualty operations, could be sold off to provide the financial leverage necessary to save taxpayers from losses from the bailout. Eleven of AIG’s subsidiaries are domiciled in Pennsylvania, including National Union Fire Insurance Co.

“There will be much interest in AIG’s life and in the AIG property-casualty companies,” Ario said at the time. “If we can start the right kind of competition, start a bidding war and make companies bid on these assets, we can go a long way to paying back that money.”

Pennsylvania officials declined comment on the Bernstein report, according to the New York Times.

New York insurance authorities, who regulate a number of AIG subsidiaries, said they were “taking this seriously,” but declined comment until they completed their review of the Bernstein report, the New York Times said.

As part of an unrelated project seeking to determine if American insurers would be able to raise stock prices soon, the report’s author, Todd R. Bault, found some data that “made no sense,” according to the New York Times report.

That led him to investigate AIG’s history of setting aside reserves over the last decade, and he found a shortfall that was big enough to alter the industry as a whole, the newspaper’s report said.

“At a minimum, if these results are reasonable, AIG would likely have to take some kind of reserve charge” if it wanted to take Chartis to an initial public offering, according to the newspaper’s report. An IPO would enable the insurer to obtain funds necessary to repay the government. However, Bault suggested, according to the Times report, that to make an IPO attractive, the insurer would need to boost its reserves. That addition would cause shares to be valued at about $10 each, about one third of the market value of the company, he estimated.

Bault’s report did not offer reasons for why AIG may have allowed the shortfall, but did say it may have changed courses after Maurice R. Greenberg, its longtime CEO, was forced out in 2005, according to the newspaper.

Another possibility, Bault said, according to the Times, was that AIG was using about half the reinsurance it used to 10 years ago, meaning it was exposing itself to more risk now than it would have in the late 1990s. If that is the case, then greater reserves would be necessary, he suggested.