limited utility of certain species may also keep 
some timber beyond economic access. In mixed 
stands, moreover, trees of inferior species or poor 
quality are often lost if they cannot be marketed 
along with the better trees. 
Although the aggregate effect of these factors 
cannot be dependably estimated, it is important 
to make allowance for economic unavailability in 
calculating allowable cut or establishing growth 
goals. 
Miscellaneous Publication 668, U. S. Department of Agriculture 
