Generally accepted accounting principles (GAAP) require, in most cases, that capital assets be depreciated. Depreciation is the systematic and rational allocation of the historical cost of a capital asset over its useful life. The estimated useful life assigned to a capital asset will directly affect the amount of depreciation expense reported each period in an accrual-based operating statement. Therefore, it is important to the quality of financial reporting that governments establish reasonable estimates of the useful lives of all of their depreciable capital assets.
The best source of relevant information on the estimated useful lives of a governments capital assets normally is its own past experience with similar assets. In situations where the documentation of a governments own past experience for a given type of capital asset is not adequate for this purpose, a government should profit as much as possible from the experience of other governments and private-sector enterprises. At the same time, a government should make whatever adjustments are needed to estimated useful lives that were obtained from others to ensure that such estimates are appropriate to its own particular circumstances. It is especially important that a government consider the potential effect of each of the following factors when depending on the experience of others:
- Quality. Similar assets may differ substantially in quality, and hence in their useful lives, because of differences in materials, design and workmanship. For example, an asphalt road will not have the same useful life as a concrete road. Likewise, the depth of the material used for paving purposes, as well as the quality of the underlying base, will also affect the useful life of a road;
- Application. The useful life of a given type of capital asset may vary significantly depending upon its intended use. For example, a residential street may be expected to have a longer useful life than a major arterial thoroughfare because of differences in the type and volume of traffic; and
- Environment. Environmental differences among governments can have an important impact on the useful lives of their respective capital assets. For instance, the useful life of a road in a climate subject to extremes in temperature is likely to be different from that of a similar road located in a more temperate climate. Also, regulatory obsolescence may shorten the service life of some capital assets used in connection with highly regulated activities (e.g., utilities).
The potential effect of each of the factors just described may be mitigated or exacerbated as a consequence of a governments maintenance and replacement policy. For example, the potential for road damage is increased in a cold environment when cracks are not promptly repaired, because water settling in the cracks will expand and contract, thereby accelerating the initial deterioration represented by the crack itself.
Once established, estimated useful lives for major categories of capital assets should be periodically compared with a governments actual experience and appropriate adjustments should be made to reflect this experience.
Depreciation is a financial reporting concept. Therefore, all of the considerations just discussed are only of concern to the extent that they could have a material impact on a governments financial statements.