This excerpt taken from the NDAQ 10-K filed Mar 15, 2006.
Sublease Loss Reserves
At December 31, 2005 and 2004, the estimated sublease loss reserve for all subleased properties was approximately $23.2 million and $36.7 million, respectively, and are included in accounts payable and accrued expenses and other liabilities in the Consolidated Balance Sheets. The reserve is adjusted throughout the year to reflect interest accretion, rental payments made during the year, depreciation on leasehold improvements if applicable and sublease receipts. The estimated losses were calculated using a 7.5% net discount rate and estimated sublease terms ranging from 5 years to 20 years at estimated market rates.