TIDEWATER INC. NOTES TO CONSOLIDATED FINANCIAL STATEMENTS Years ended March 31, 2010, 2009, and 2008  could result in the inability to recover the current carrying value of an asset group, thereby possibly requiring  an impairment charge in the future. As the company’s fleet continues to age, management closely monitors  the estimates and assumptions used in the impairment analysis to properly identify evolving trends and  changes in market conditions that could impact the results of the impairment evaluation.  The company performs a periodic impairment review of its stacked vessels and vessels withdrawn from  service. This review is undertaken every six months, or more often if considered necessary, and considers  items such as the vessel’s age, length of time stacked and likelihood of a return to service, among others.  The company records an impairment charge when the carrying value of a vessel withdrawn from service or  a stacked vessel that is unlikely to return to service exceeds its estimated fair value. The company recorded  impairment charges of $3.1 million and $1.4 million during fiscal 2010 and 2009, respectively, which is  included in gain on asset dispositions, net. No impairment was recorded during fiscal 2008.  Goodwill represents the cost in excess of fair value of the net assets of companies acquired. The company  does not amortize goodwill, but tests goodwill annually for impairment (or on a more frequent basis if events  or changes in circumstances indicated that the carrying amount of the reporting unit exceeds its fair value)  using a fair value-based approach. An impairment loss would be recorded if the recorded goodwill exceeds  its implied fair value. Goodwill primarily relates to the fiscal 1998 acquisition of O.I.L. Ltd., a British company.  Goodwill of $279.4 million and $49.4 million, respectively, is assigned to the International and United States  reporting units. Although the assets and liabilities acquired in the acquisition of O.I.L., Ltd. were primarily  assigned to the International reporting unit, a portion of the goodwill was allocated to the United States  reporting unit following the acquisition based on the estimated increase in the fair value of that reporting unit.  At March 31, 2010, the company’s goodwill represented 10% of total assets and 13% of stockholders’  equity. No impairment of goodwill was recorded during fiscal 2010, 2009 and 2008. The company's insurance subsidiary establishes case-based reserves for estimates of reported losses on  direct business written, estimates received from ceding reinsurers, and reserves based on past experience  of unreported losses. Such losses principally relate to the company's marine operations and are included as  a component of costs of marine operations in the consolidated statements of earnings. The liability for such  losses and the related reimbursement receivable from reinsurance companies are classified in the  consolidated balance sheets into current and noncurrent amounts based upon estimates of when the  liabilities will be settled and when the receivables will be collected. The company follows the provisions of Compensation – Retirement Benefits, ASC Topic 715, and uses a  March 31 measurement date for determining net periodic benefit costs, benefit obligations and the fair value  of plan assets. Net periodic pension costs and accumulated benefit obligations are determined using a  number of assumptions including the discount rates used to measure future obligations and expenses, the  rate of compensation increases, retirement ages, mortality rates, expected long-term return on plan assets,  health care cost trends, and other assumptions, all of which have a significant impact on the amounts  reported. The company’s pension cost consists of service costs, interest costs, expected returns on plan assets,  amortization of prior service costs or benefits and, in part, on a market-related valuation of assets. The  company considers a number of factors in developing its pension assumptions, including an evaluation of  relevant discount rates, expected long-term returns on plan assets, plan asset allocations, expected  changes in wages and retirement benefits, analyses of current market conditions and input from actuaries  and other consultants. Net periodic benefit costs are based on a market-related valuation of assets equal to the fair value of assets.  For the long-term rate of return, assumptions are developed regarding the expected rate of return on plan  assets based on historical experience and projected long-term investment returns, which consider the plan’s  F-11 Pension and Other Postretirement Benefits Accrued Property and Liability Losses  Goodwill 