as previously permitted. 

Stock-based compensation was $101 million, $87 million and $58 million during 2006, 2005, and 2004. We applied the fair value accounting provisions of SFAS No. 123(R) for 2006 and 2005 compared with the application of APB Opinion No. 25, including variable accounting treatment on certain awards, for 2004. Because of the application of different methods of accounting as well as the effects of variable accounting treatment in 2004, stock-based compensation for 2006 and 2005 is not comparable to prior periods. As of December 31, 2006, there was $217 million of net unrecognized compensation cost, related to unvested stock-based compensation arrangements. 

Other Operating Expense (Income) 

Other operating expense was $10 million in 2006, primarily attributable to amortization of other intangibles. Other operating expense was $47 million in 2005, primarily attributable to our settlement of a patent lawsuit for $40 million, as well as amortization of other intangibles of $5 million. Other operating income was $8 million for 2004, which includes net restructuring-related credits of $9 million and amortization of other intangibles of $1 million. 

During 2004, we determined that certain of the office space previously vacated as part of our 2001 restructuring was necessary for our future needs. We reduced our restructuring-related liability resulting in a gain of $13 million for 2004. Lease payments for this office space are expensed over the lease period and classified to the corresponding operating expense categories on our consolidated statements of operations. 

In 2004, we streamlined our organizational structure in France to reduce our operating costs. This reduction resulted in severance costs of $4 million classified in “Other operating expense (income)” on our consolidated statements of operations. 

Income from Operations 

Income from operations was $389 million, $432 million, and $440 million during 2006, 2005, and 2004. The decrease in 2006 from 2005 is primarily a result of an increase in spending for technology and content. The decrease in 2005 from 2004 is primarily a result of an increase in spending for technology and content, an increase in stock-based compensation that is now recorded under SFAS No. 123(R) fair value accounting, and a payment of $40 million to settle a patent lawsuit. These increased expenditures were partially offset by higher net sales and gross profit. 

Interest Expense and Income 

The primary component of our net interest expense is the interest we incur on our long-term debt instruments, including a $900 million principal balance of our 4.75% U.S. Convertible Subordinated Notes and a €240 million ($317 million based on the exchange rate at December 31, 2006) principal balance of our 6.875% PEACS at December 31, 2006. Interest expense was $78 million, $92 million, and $107 million in 2006, 2005, and 2004, with declines primarily relating to principal repayments of $300 million, $265 million, and $150 million in 2006, 2005, and 2004. 

At December 31, 2006, our total long-term indebtedness was $1.25 billion compared to $1.48 billion at December 31, 2005. See Item 8 of Part II,