2009, 2008, and 2007 with the decline primarily relating to principal reductions of $319 million in 2009 and $899 million in 2008. 

Our long-term debt was $109 million and $409 million at December 31, 2009 and 2008. See Item 8 of Part II, “Financial Statements and Supplementary Data—Note 5—Long-Term Debt.” 

Income Taxes

We recorded a provision for income taxes of $253 million, $247 million, and $184 million, in 2009, 2008, and 2007. The effective tax rate in 2009, 2008 and 2007 was lower than the 35% U.S. federal statutory rate primarily due to earnings of our subsidiaries outside of the U.S. in jurisdictions where our effective tax rate is lower than in the U.S. 

Our effective tax rate is subject to significant variation due to several factors, including our accuracy in predicting our taxable income, the taxable jurisdictions to which it relates, business acquisitions and investments, and foreign currencies. We have current tax benefits, net operating losses, and tax credits relating to excess stock-based compensation deductions that are being utilized to reduce our U.S. taxable income. As such, we expect a majority of our net tax provision to be non-cash. 

Non-GAAP Financial Measures 

Regulation G, Conditions for Use of Non-GAAP Financial Measures , and other SEC regulations define and prescribe the conditions for use of certain non-GAAP financial information. Our measure of “Free cash flow” meets the definition of a non-GAAP financial measure. Free cash flow is used in addition to and in conjunction with results presented in accordance with GAAP and free cash flow should not be relied upon to the exclusion of GAAP financial measures. 

Free cash flow, which we reconcile to “Net cash provided by (used in) operating activities,” is cash flow from operations reduced by “Purchases of fixed assets, including internal-use software and website development.” We use free cash flow, and ratios based on it, to conduct and evaluate our business because, although it is similar to cash flow from operations, we believe it typically will present a more conservative measure of cash flows since purchases of fixed assets are a necessary component of ongoing operations. 

Free cash flow has limitations due to the fact that it does not represent the residual cash flow available for discretionary expenditures. For example, free cash flow does not incorporate payments made on capital lease obligations or cash payments for business acquisitions. Therefore, we believe it is important to view free cash flow as a complement to our entire consolidated statements of cash flows. 

In addition, we provide information regarding our operating expenses with and without stock-based compensation. We provide this information to show the impact of stock-based compensation, which is non-cash and excluded from our internal operating plans and measurement of financial performance (although we consider the dilutive impact to our shareholders when awarding stock-based compensation and value such awards accordingly). In addition, unlike other centrally-incurred operating costs, stock-based compensation is not allocated to segment results and therefore excluding it from