454 ESTIMATION OF INCREMENT 



In this instance, the difference in the percentage thus 

 indicated, after taking into consideration the value of the 

 land and the annual outgoings, is somewhat large ; but, this 

 difference is very much less when the value of the crop 

 largely exceeds that of the land only ; and becomes less as 

 the value of the crop becomes larger. 



In cases where a thinning has taken place during the 

 period under consideration, it will be necessary to ascertain 

 the sum to which the money value of that which was thinned 

 out will amount at compound interest (say 3^ per cent.) by 

 the end of the period, and to add this sum to the increment 

 in value of the rest of the crop, and also to the mean capital 



as found by the formula. 



Thus, taking the previous example, let it be supposed 

 that in 4 years' time 6 worth be removed by a thinning. 

 This 6 will amount, in the remaining 6 years of the period 

 at 3i per cent, compound interest, to ^7-37. 



Hence the percentage will be 



200* x 41-6+7-37 

 n 59 +100-6 + 7-37 



= 200 x m g 



10 166-97 



* Wherever the -^ formula is used, the percentage shown will be slightly 

 n 



less than the true mathematical percentage yielded. 



Finally, it is well to remember that, when considering the 

 treatment that any crop should receive, conclusions should 

 not be hastily drawn from actuarial data alone. It is 

 necessary to consider the particular demands of the species 

 of trees, the quality of the timber, the condition of the 

 soil, local markets, and many other details, which the circum- 

 stances of the case may suggest. 



But, after giving due weight to all other considerations, 

 actuarial calculations must largely govern the treatment that 

 is meted out to any particular crop. 



When the increment in quantity and value on any crop 

 s not sufficient, it is imperative that some action should be 



