472 MISC. PUBLICATION 218, U. S. DEPT. OF AGRICULTURE 
yields the corresponding management costs, net yields, and assessment 
values. Such tables are available in appendix 1 of the circular of 
August 6, 1931, for each of the five forest regions. 
IRREGULAR Forests Wi1TH WoRKING PLANS 
In the case of forests with an irregular distribution of age classes, 
the procedure is not quite so simple. It involves the appraisal of 
each age class in accordance with its relation to a stand similar in 
site quality, species, market conditions, and length of rotation, but 
with a normal distribution of age classes. The first step, then, is 
to determine the value of a normal forest in the same region that 
resembles in these respects the forest being valued. If there is a 
sufficiently similar forest in the district to serve as a basis of valua- — 
tion, this forest is used for the purpose. Otherwise the yield of an 
imaginary forest must be calculated from yield tables, with suitable 
deductions to allow for loss in cutting and for the difference between 
the ideal and actual practice. Care is taken to apply to the average 
yield in wood, prices which correctly reflect the values of the grades 
which would be realized in a normal forest rather than the values of 
grades actually realized in the irregular forest, which might be either 
much higher or much lower. Having the gross yield in money of 
the corresponding normal forest, the assessment value per hectare 
of such a forest is determined as previously indicated. 
The next step is to determine what part of the value of the similar 
normal forest is represented by the age classes present in the actual 
forest which is to be assessed. ‘This step is accomplished by using a 
set of tables which shows the relative value of each age class. This 
set of tables is made on the theory that the total yield value of a 
normal sustained-yield forest may be allocated to the age classes 
into which it is divided in proportion to the relative market value 
of each. ‘The values of the single-age classes are added together to 
give a total, and the value of each age class calculated as a percentage 
of the whole. 
For the purpose of establishing the market value, each age class 
beginning with 40 years in the normal forest is valued according to 
the sale price of the timber plus the value of bare land. The value 
of the forest in age classes younger than 40 years is calculated from 
the market value at 40 years (Ag) by Glaser’s formula: 
Ag—C °9 
Ais Tag7 ya +C, 
in which A, is the value at a given age, 7, and C is the initial cost of 
planting or of establishing the stand (248, p. 93). The results 
obtained from this formula are checked and corrected by considera- 
tion of sales prices. How bare-land value is obtained is not explained 
in the official documents, but it is understood to be based in part on 
sales data, assuming that the difference between the selling price of 
a forest and the value of the timber which it contains equals the 
bare-land value. 
For the 1931 assessment, tables have been prepared showing value 
relationships of the age classes for each of the common species: 
Oak, beech, elm, plains spruce, mountain spruce, fir, and pine. 
These are published as appendix 3 of the circular of August 6. 19st 
