[] () a way of reducing the value of (depreciating) an asset in a company's financial records in which the amount taken from the asset's value decreases each year. The value of the asset (its book value) is reduced at a fixed rate each year, calculated as the difference between the original value of the asset and its final ( residual) value, divided by a particular number of years and multiplied by two.加倍余额递减法；双倍余额递减法➡reducing balance method , straight-line method , sum of the digits method