NORMAL YIELD AND GROWING STOCK. 251 



Cubic feet- 

 Every year a wood 100 years old is cut over, giving = 5580 



Normal annual yield = 5580 



Total mean annual increment = 55'8 x 100 . . = 5580 

 current -10(51 + 78 + 85 + 76 



+ 63 + 53 + 47 + 42 

 + 35 + 28) = 

 558x10 . . = 5580- 



4. Relation between Normal Yield and Normal Groiving Stock. 



If the normal yield (FJ is divided by the normal growing 

 stock (6r n ) and the quotient multiplied by 100, the result ia 



called the " utilization per cent." 



Y 

 Utilization per cent. = -2. x 100. 



(jr n 



It gives the units of yield for every 100 units of growing 

 stock, just as the increment per cent, gives the units of incre- 

 ment for every 100 units of growing stock. As the increment 

 of a whole series of age gradations is equal to the yield of the 

 same, it follows that 



Utilization per cent. = increment per cent, of the whole 



series of age gradations. 

 Placing the current annual increment equal to the mean 



r X / 

 annual increment, and calculating G n for summer = -- ,. 



the utilization per cent, for the rotation of the maximum 

 volume production is always equal to twice the increment 

 per cent, of the oldest age gradation. It has been shown 

 above (page 187) that for the year in which the mean annual 

 increment culminates (rotation of maximum volume produc- 

 tion), the 



100 

 Increment per cent. = . 



For the same rotation 



Utilization per cent. = * x 100 = ~ X 10 

 G rxl 



