We do not utilize financial instruments for trading purposes and hold no derivative financial instruments, other financial instruments or derivative commodity instruments that could expose us to significant market risk other than our investments disclosed in “Fair Value Measurements” in Note 4 to the Consolidated Financial Statements. We generally invest in investment grade financial instruments to reduce our exposure related to investments. Our primary market risk exposure with regard to such financial instruments is to changes in interest rates, which would impact interest income earned on investments. However, based upon the conservative nature of our investment portfolio and current experience, we do not believe a decrease in investment yields would have a material negative effect on our interest income. 36 Substantially all our revenue is derived from outside of North America and primarily denominated in U.S. dollars and therefore we bear no significant foreign exchange risk from routine customer sales transactions. However, due to a withholding tax receivable denominated in Korean Won, we do bear foreign exchange risk from fluctuations in the Korean Won to U.S. dollar exchange rate and resulting remeasurement.