The 3G concession is valid through December 31, 2018. The 3G concession fee is amortized on a straight- line basis from the date operations commence through the date the license expires. Computer software costs  and patents are amortized using the straight-line method over the estimated useful lives of 2 to 20 years.  Expenditure on research shall be expensed as incurred. Development costs are capitalized when those  costs meet relative criteria and are amortized using the straight-line method over estimated useful lives.  Development costs that do not meet relative criteria shall be expensed as incurred.  When an indication of impairment is identified for intangible assets other than goodwill, any excess of the  carrying amount of an asset over its recoverable amount is recognized as a loss. If the recoverable amount  increases in a subsequent period, the amount previously recognized as impairment would be reversed and  recognized as a gain. However, the adjusted amount may not exceed the carrying amount that would have  been determined, as if no impairment loss had been recognized.  Goodwill represents the excess of the consideration paid for business acquisition over the fair value  of identifiable net assets acquired. Goodwill is tested for impairment annually. If an event occurs or  circumstances change which indicates that the fair value of goodwill is below its carrying amount, an  impairment loss is recognized. A subsequent reversal of such impairment loss is not allowed.  Idle assets are carried at the lower of recoverable amount or carrying amount.  For defined benefit pension plans, net periodic pension benefit cost is recorded in the consolidated statement  of income and includes service cost, interest cost, expected return on plan assets, amortization of prior service  costs, amortization of pension gains ( losses) and curtailment or settlement gains ( losses).  The Company recognizes into income, any unrecognized actuarial net gains or losses that exceed 10% of  the larger of projected benefit obligations or plan assets, defined as the “corridor”. Amounts inside this 10%  corridor are amortized over the average remaining service life of active plan participants. Actuarial net gains  and losses occur when actual experience differs from any of the many assumptions used to value the plans.  Differences between the expected and actual returns on plan assets and changes in interest rate, which affect  the discount rate used to value projected plan obligations, can have a significant impact on the calculation of  pension net gains and losses from year to year.  The curtailments and settlement gains (losses) resulted from the Chunghwa’s early retirement programs.  Curtailment/settlement gains or losses are equal to the changes of underfunded status plus a pro rata  portion of the unrecognized prior service cost, unrecognized net gains (losses), and unrecognized transition  obligations/assets, before the settlement/curtailment event multiplied by the percentage reduction in projected  benefit obligation.  The projected benefit obligation represents the actuarial present value of benefits expected to be paid upon  retirement based on estimated future compensation levels.  The carrying amount of accrued pension liability should be the sum of the following amounts when the  calculation is positive: (a) projected benefit obligation as of balance sheet date, (b) minus (plus) unamortized  actuarial loss (gain), (c) minus unamortized prior service cost, and (d) minus the fair value of plan assets. If  the amount determined by above calculation is negative, it is viewed as prepaid pension cost. The prepaid  pension cost is measured at the lower of: (a) the amount determined above, and (b) the sum of the following  amounts: (i) unamortized actuarial loss, (ii) unamortized prior service cost, and (iii) the present value of  refunds from the plan or reductions in future contributions to the plan.  F-24 Pension Costs  Idle Assets 