outside of the U.S. of $2.1 billion. Cash taxes paid (net of refunds) were $112 million, $33 million, and $75 million for 2012, 2011, and 2010. As of December 31, 2012, our federal net operating loss carryforward was approximately $89 million. We also have approximately $136 million of federal tax credits potentially available to offset future tax liabilities. As we utilize our federal tax credits, we expect cash paid for taxes to significantly increase. We endeavor to optimize our global taxes on a cash basis, rather than on a financial reporting basis. 

See Item 8 of Part II, “Financial Statements and Supplementary Data—Note 8—Commitments and Contingencies” for additional discussion of our principal contractual commitments, as well as our pledged securities. Purchase obligations and open purchase orders, consisting of inventory and significant non-inventory commitments, were $3.8 billion at December 31, 2012. Purchase obligations and open purchase orders are generally cancelable in full or in part through the contractual provisions. 

On average, our high inventory velocity means we generally collect from consumers before our payments to suppliers come due. Inventory turnover was 9, 10, and 11 for 2012, 2011, and 2010. We expect 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 and selection of product offerings, our investment in new geographies and product lines, and the extent to which we choose to utilize outsource fulfillment providers. 

We believe that cash flows generated from operations and our 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 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 Officer reviews our operating results in assessing performance and allocating resources. 

Net Sales 

Sales increased 27%, 41%, and 40% in 2012, 2011, and 2010, compared to the comparable prior year periods.