At each balance date, the useful lives and residual values of property plant and equipment and intangible assets are reviewed. Assessing the appropriateness of useful life and residual value estimates of property, plant and equipment and intangible assets requires several factors to be considered such as the physical condition of the asset, expected period of use of the asset by the Commission, and expected disposal proceeds from the future sale of the asset. An incorrect estimate of the useful life or residual value will affect the depreciation or amortisation expense recognised in the surplus or deficit in the statement of comprehensive revenue and expense, and the carrying amount of the asset in the statement of financial position. Notes 8 and 9 detail the carrying amounts of property, plant and equipment and intangible assets respectively. Retirement and long-service leave Note 7 details the critical estimates and assumptions made in relation to retirement and long service leave liabilities. Comparative information When presentation or classification of items in the financial statements is amended or accounting policies are changed voluntarily, comparative figures are restated to ensure consistency with the current period unless it is impracticable to do so. There have been no restatements of comparative information in the financial statements. 2 Revenue 2020 $000 2019 $000 14,518 9,396 27 220 14,545 9,616 93 82 Other revenue 139 253 Total revenue from exchange transactions 232 335 14,777 9,951 Revenue from non-exchange transactions Revenue from the Crown Other revenue Total revenue from non-exchange transactions Revenue from exchange transactions Interest received Total revenue 46 Human Rights Commission Annual Report 2019/20