CHAPTER V
ELEMENTS WHICH REDUCE VALUE
Deductions from Value
The Lessening of Worth. — The value of a property may increase
 or decrease with age. Having in the preceding chapter
called attention to the essentials of value and to certain elements
which add value, there will be considered briefly in this chapter
some of the factors which reduce value.
In the case of any operating plant there will be parts which
deteriorate or wear out under the effect of continued use. By
ordinary care the rate at which the perishable parts of a plant
are consumed in rendering useful service is held at or near the
average rate which experience teaches should be regarded as
inevitable. If ordinary care is not exercised and a plant by
reason of neglect gets into a condition which requires special
attention to restore it to an average condition, all circumstances
of use and age being considered, the prospective outlay to accomplish
 this rehabilitation is called deferred maintenance. But
even when there is no deferred maintenance there may have
been a lessening of worth due to the fact that on account of
wear and tear, or by reason of obsolescence, or inadequacy,
or from any other cause, the time of probable serviceability of
any article in question is being continually lessened. Loss of
value from such cause is depreciation. Or again, if cost is made
a starting point, it may be found that there is included unused
property perhaps held to meet a future demand, but which,
when valuations as a basis for rates are under consideration,
may have to be omitted or deducted from the aggregate of the
listed properties. And, finally, the property under consideration
 may include items designed of a capacity to meet future
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