The concept of the internal rate can be defined as the rate of interest, which if applied to expenditures incurred at different times, gives a compounded sum equal to revenues compounded at the same rate for the same time. This concept has long been used in forestry, particularly concerning the development of a stand, because in this case there is a time difference between many items of expenditure and revenue. Several terms have been used or the notions derived on this basis. The term internal rate of return has begun to appear only recently. This article explains different variations of the concept and its different names, together with some related concepts and terms.
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