in compliance with our investment policy.  As of January 27, 2013, our investments in U.S. government agencies and U.S. government sponsored enterprises represented approximately 56% of our total investment portfolio, while the financial sector accounted for approximately 19% of our total investment portfolio. All of our investments are with A/A2 or better rated securities.



We performed an impairment review of our investment portfolio as of January 27, 2013.  Based on our quarterly impairment review, we concluded that our investments were appropriately valued and did not record any impairment during fiscal year 2013.   



Net realized gains were $0.5 million, $0.4 million and $1.5 million for fiscal years 2013, 2012 and 2011, respectively.  As of January 27, 2013, we had a net unrealized gain of $10.9 million, which was comprised of gross unrealized gains of $11.7 million, offset by $0.8 million of gross unrealized losses.  As of January 29, 2012, we had a net unrealized gain of $11.5 million, which was comprised of gross unrealized gains of $12.0 million, offset by $0.5 million of gross unrealized losses. 



Our accounts receivable are highly concentrated and make us vulnerable to adverse changes in our customers’ businesses, and to downturns in the industry and the worldwide economy.  Three customers accounted for approximately 40% of our accounts receivable balance at January 27, 2013. While we strive to limit our exposure to uncollectible accounts receivable using a combination of credit insurance and letters of credit, difficulties in collecting accounts receivable could materially and adversely affect our financial condition and results of operations. These difficulties are heightened during periods when economic conditions worsen. We continue to work directly with more foreign customers and it may be difficult to collect accounts receivable from them. We maintain an allowance for doubtful accounts for estimated losses resulting from the inability of our customers to make required payments. This allowance consists of an amount identified for specific customers and an amount based on overall estimated exposure. If the financial condition of our customers were to deteriorate, resulting in an impairment in their ability to make payments, additional allowances may be required, we may be required to defer revenue recognition on sales to affected customers, and we may be required to pay higher credit insurance premiums, any of which could adversely affect our operating results. In the future, we may have to record additional reserves or write-offs and/or defer revenue on certain sales transactions which could negatively impact our financial results.



Our cash balances are held in numerous locations throughout the world, including substantial amounts held outside of the United States. As of January 27, 2013, we had cash, cash equivalents and marketable securities of $1.80 billion held within the United States and $1.93 billion held outside of the United States.  Most of the amounts held outside the United States may be repatriated to the United States but, under current law, would be subject to U.S. federal income taxes, less