The documents obtained by Thomson Reuters' private equity website peHUB show that the $26b (£15.84b) deal to buy Hilton at the peak of the market in July 2007 is now worth only half the amount originally estimated by Blackstone after the hotel market has weathered the economic crisis.
Blackstone, which became a publicly traded company in June 2007, discloses how it is valuing individual companies to the investors in its funds. The documents obtained are labelled "Highly Confidential & Trade Secret".
Blackstone declined to comment on the documents.
Funds revalue their investments on a quarterly basis, and given the rebound in equity markets in the past few months, it is possible some investments have since been marked higher.
The fall is similar to the fall seen in the share price of publicly-listed rival Marriott Hotels which is trading about half its July 2007 level.
By Gemma Sharkey
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