availability, which enables faster delivery of products to our customers. We expect some variability in inventory turnover over time as it is affected by several factors, including our product mix, the mix of sales by us and by other sellers, our continuing focus on in-stock inventory availability, our investment in new geographies and product lines, and the extent to which we choose to utilize outsource fulfillment providers. 

Pledged Securities 

We are required to pledge or otherwise restrict a portion of our cash and marketable securities as collateral for standby letters of credit, guarantees, debt, and real estate leases. We classify cash and marketable securities with use restrictions of twelve months or longer as non- current “Other assets” on our consolidated balance sheets. The balance of pledged securities at December 31, 2008 consisted of $308 million included in “Other assets.” The amount required to be pledged for certain real estate lease agreements changes over the life of our leases based on our credit rating and changes in our market capitalization (common shares outstanding multiplied by the closing price of our common stock). 

We believe that current cash, cash equivalents, and marketable securities balances will be sufficient to meet our anticipated operating cash needs for at least the next 12 months. However, any projections of future cash needs and cash flows are subject to substantial uncertainty. See Item 1A of Part I, “Risk Factors.” We continually evaluate opportunities to sell additional equity or debt securities, obtain credit facilities, repurchase common stock, pay dividends, or repurchase, refinance, or otherwise restructure our long-term debt for strategic reasons or to further strengthen our financial position. The sale of additional equity or convertible debt securities would likely be dilutive to our shareholders. In addition, we will, from time to time, consider the acquisition of, or investment in, complementary businesses, products, services, and technologies, which might affect our liquidity requirements or cause us to issue additional equity or debt securities. There can be no assurance that additional lines-of-credit or financing instruments will be available in amounts or on terms acceptable to us, if at all. 

Results of Operations 

We have organized our operations into two principal segments: North America and International. We present our segment information along the same lines that our chief executive reviews our operating results in assessing performance and allocating resources. Our period-over- period revenue growth was 26% in 2006, 39% in 2007 and 36% for the first three quarters of 2008. For Q4 2008, our quarterly revenue growth rate declined to 18%, driven primarily by decreased consumer demand following disruptions in the global financial markets and changes in foreign exchange rates (excluding the $320 million unfavorable impact from year-over-year changes in foreign exchange rates throughout the fourth quarter, net sales would have grown 24% compared with Q4 2007). See Item 8 of Part II, “Financial Statements and Supplementary Data—Note 14—Quarterly Results (Unaudited).” 

Net