are based on the expected costs of investigation and remediation and the likelihood that other potentially responsible parties will be able to fulfill their commitments at sites where we may be jointly or severally liable. At the time a liability is recorded for future environmental costs, we record an asset for estimated future recoveries that are estimable and probable. Some of our environmental costs are eligible for future recovery in the pricing of our products and services to the U.S. government and under existing third party agreements. We consider the recovery probable based on the Global Settlement, U.S. government contracting regulations, and our long history of receiving reimbursement for such costs. We file a consolidated U.S. federal income tax return for the Company and our 100% owned consolidated subsidiaries. The deferred tax assets and/or liabilities are determined by multiplying the differences between the financial reporting and tax reporting bases for assets and liabilities by the enacted tax rates expected to be in effect when such differences are recovered or settled. The effect on deferred taxes of a change in tax rates is recognized in the period of the enactment date of the change. The carrying value of our deferred tax assets is dependent upon our ability to generate sufficient taxable income in the future. A valuation allowance is required when it is more likely than not that all or a portion of a deferred tax asset will not be realized. A review of all available positive and negative evidence is considered, including our past and future performance, the market environment in which we operate, the utilization of tax attributes in the past, the length of carryback and carryforward periods, and evaluation of potential tax planning strategies. We believe that certain positions may be challenged by taxing authorities. Settlement of any challenge can result in no change, a complete disallowance, or a partial adjustment reached through negotiations or litigation. Our tax reserves reflect the difference between the tax benefit claimed on tax returns and the amount recognized in the financial statements. The accounting standards provide guidance for the recognition and measurement in financial statements of uncertain tax positions taken or expected to be taken in a tax return. The evaluation of a tax position is a two-step process, the first step being recognition. We determine whether it is more likely than not that a tax position will be sustained upon tax examination, including resolution of any related appeals or litigation, based on only the technical merits of the position. The technical merits of a tax position are derived from both statutory and judicial authority (legislation and statutes, legislative intent, regulations, rulings, and case law) and their applicability to the facts and circumstances of the tax position. If a tax position does not meet the more likely than not recognition threshold, the benefit of that position is not recognized in the financial statements. The second step is measurement. A tax position that meets the more likely than not recognition threshold is measured to determine the amount of benefit to recognize in the financial statements. The tax position is measured as the largest amount of benefit that is greater than 50% likely of being realized upon ultimate resolution with a taxing authority. As the examination process progresses with tax authorities, adjustments to tax reserves may be necessary to reflect taxes payable upon settlement. Tax reserve adjustments related to positions impacting the effective tax rate affect the provision for income taxes. Tax reserve adjustments related to positions impacting the timing of deductions impact deferred tax assets and liabilities. 36 Income Taxes