FOREST PER CENT 79 



The above formula may also be written : 



p =I(X?r ,-+S-t-K \ 



vVs+c+E ; 



which is nothing more than the old form of the Weiser per cent, 

 where the period includes the entire rotation, c the cost of planting 

 represents the value of the stand just planted or at the beginning, 

 and Yr is the value of the stand at the end of the period. 



Whether the value of the land is taken at cost, sale or expecta- 

 tion value is optional. Certainly the introduction of Se means the 

 use of a maximum which is not to be recommended. Since the val- 

 ues of land are apt to change very decidedly during a period of 

 eighty years it is not only permissible but even proper to set a higher 

 value for S in the numerator, i. e., in the final capital, than in the 

 denominator or initial capital. 



In some recent publications the formula is written in a modified 

 form as : 



Yr 4- S Ei i.op r i 



i.op r =: c . ~ and Ex is equivalent to e 



i. op i 



or merely the end value of all expenses during this one rotation com- 

 pounded at ordinary interest rate, the assumption being that money 

 is borrowed (actually or not) at ordinary rates for this purpose of 

 paying taxes, protection, etc. It is evident that this, as well as many 

 other forms, is possible and that some uniformity in the use of the 

 letters and writing of these formulae will greatly help all concerned. 

 Where thinnings are made, and this must be assumed as the 

 normal condition in forestry, the above formula is incomplete and 

 must be modified to take care of the receipts from thinnings. This 

 may be done as follows : 



Yr + S Tq(i.opr-q)+ Sc -J- E 

 I " opf .c + Sc + E 



2. Rate of interest made by a regulated forest, or one pro- 

 ducing a regular yearly income. 



Since the yearly net income is in the nature of interest on the 

 capital invested in the forest and since this income is known, it is 

 necessary only to determine the value of the property, stand, and 

 land. But as this may be cost, sale, or expectation value of either 

 land or stand, a variety of conditions are possible. 



Where the forest has been purchased in recent time, where the 

 income so far received has paid all expenses including an acceptable 

 rate of interest, and where the management has prevented any de- 



