368 lotka: efficiency in organic evolution 



The quantity Vi in equation (15) has an interesting economic 

 significance. It is the (negative) value, per unit, of the impre- 

 cision denoted by the parameter /. Thus if / is short-sighted- 

 ness, measured, say, in dioptries of the correcting lens, then 

 Vi di is the (annual) loss in values (commodities) which would 

 be suffered, per head, if all individuals had their short-sighted- 

 ness increased by a small increment 8i, all other .things remaining 

 the same. 



Or, putting it in another way, Vi di is the /air compensation^^ 

 which should be paid, per head, to a community in which each 

 individual had his eyesight injured by the (infinitesimal) incre- 

 ment 8i, in order to restore to them the total earnings (measured 

 in real commodities) which they made prior to the injury. 



Equations (9), (14), and (15) represent the solution of the 

 problem of finding an expression for the differential coefficient 

 (1), so far as errors of observation, operation and mentation are 

 concerned. 



" To prevent any possible misunderstanding, it must here be pointed out 

 that we cannot, along the lines here given, establish an exact expression for the 

 fair compensation corresponding to an injury di for the case of one individual so 

 injured and competing with others not injured. 



