Investments Income Taxes 155 We are required to establish a valuation allowance against our  deferred tax asset (“DTA”) when it is more likely than not  that all or some portion of our DT A will not be realized. At each balance sheet date, we assess our need for a valuation  allowance and this assessment is based on all available evidence, both positive and negative, and requires management to  exercise judgment and make assumptions regarding whether such DT A will be realized in future periods. Future realization of  our DTA will ultimately depend on the existence of suf ficient taxable income of the appropriate character (ordinary income or  capital gains) within the applicable carryback and carryforward periods provided under the tax law . The primary sources of  negative evidence that we considered are our cumulative losses in recent years and the continued uncertainty around our future  operating results. We also considered several sources of positive evidence when assessing the need for a valuation allowance,  such as future reversals of existing taxable temporary dif ferences, future projections of taxable income, taxable income within  the applicable carryback periods and potential tax planning strategies. In making our assessment of the more likely than not  standard, the weight assigned to the ef fect of both negative and positive evidence is commensurate with the extent to which  such evidence can be objectively verified. We provide for income taxes in accordance with the provisions of the accounting standard regarding accounting for  income taxes. As required under this standard, our deferred tax assets and liabilities are recognized under the balance sheet  method, which recognizes the future tax ef fect of temporary dif ferences between the amounts recorded in our consolidated  financial statements and the tax bases of these amounts. Deferred tax assets and liabilities are measured using the enacted tax  rates expected to apply to taxable income in the periods in which the deferred tax asset or liability is expected to be realized or  settled.   In evaluating whether a decline in value is other -than-temporary, we consider several factors in addition to the above,  including, but not limited to, the following: We record an other-than-temporary impairment on a security if we intend to sell the impaired security or if it is more  likely than not that we will be required to sell the impaired security prior to recovery of its amortized cost basis, or if the present  value of cash flows we expect to collect is less than the amortized cost basis of the security . If a sale is likely, the security is  classified as other-than-temporarily impaired and the full amount of the impairment is recognized as a loss in the statement of  operations. Otherwise, losses on securities that are other -than-temporarily impaired are separated into: (i) the portion of loss  that represents the credit loss; and (ii) the portion that is due to other factors.  The credit loss portion is recognized as a loss in  the statement of operations, while the loss due to other factors is recognized in accumulated other comprehensive income (loss),  net of taxes. A credit loss is determined to exist if the present value of discounted cash flows expected to be collected from the  security is less than the cost basis of the security . The present value of discounted cash flows is determined using the original  yield of the security. For certain hybrid financial instruments that would be required to be separated into a host contract and a derivative  instrument, the accounting standard regarding derivatives and hedging permits an entity to irrevocably elect to initially and  subsequently measure that hybrid financial instrument in its entirety at fair value (with changes in fair value recognized in  earnings). We elected to record our convertible securities meeting these criteria at fair value with changes in the fair value  recorded as net gains or losses on investments. All hybrid financial instruments are classified as trading securities. We group assets in our investment portfolio into one of three main categories: held to maturity , available for sale or  trading securities. Fixed-maturity securities for which we have the positive intent and ability to hold to maturity are classified as  held to maturity and are reported at amortized cost. Investments in securities not classified as held to maturity or trading  securities are classified as available for sale and are reported at fair value, with unrealized gains and losses (net of tax) reported  as a separate component of stockholders’  equity as accumulated other comprehensive income (loss). Investments classified as  trading securities are reported at fair value, with unrealized gains and losses reported as a separate component of income. Short- term investments consist of assets invested in money market instruments, certificates of deposit  and highly liquid, interest  bearing instruments with an original maturity of three months or less at the time of purchase.  Amortization of premium and  accretion of discount are calculated principally using the interest method over the term of the investment. Realized gains and  losses on investments are recognized using the specific identification method. •  the extent and the duration of the decline in value; •  the reasons for the decline in value (e.g., credit event, interest related or market fluctuations); and •  the financial position, access to capital and near term prospects of the issuer , including the current and future impact of  any specific events.