From an individual event perspective, the resource transfer is dependent upon future events, namely future income. Further, the sacrifices of economic benefits arising from present obligations of an entity disappear or are significantly reduced if a depreciable asset is sold during its useful life for an amount less than its book value. Liability recognition is warranted only if the asset is held to the end of its useful life. Liability recognition resulting from an individual transaction depends upon aggregate future events, that is, future operational decisions regarding depreciable assets.