14 BULLETIN 1224, U. S. DEPARTMENT OF AGRICULTURE. 
A complete classification of these productivity factors is not given 
in the census publications. Such a classification by counties would 
roughly be as follows: 
LAND CLASSIFICATION. 
I. Acres of multiple use land. 
A. Acres needing drainage. 
B. Acres needing other improvements. 
II. Acres of single-use land. 
A. Acres of permanent pasture. 
1. Acres potentially multiple-use. 
a. By drainage. 
b. By clearing. 
c. By both. 
B. Acres of woods pasture. 
1. Acres potentially multiple-use. 
a. By clearing. 
b. By drainage. 
c. By both. 
C. Acres of waste land. 
YIELD FACTORS. 
I. Five or ten year average yield of major crops. 
DISTANCE FACTORS. 
I. Average distance of farms in each county to local markets. 
II. Distance of county to central market. 
ROAD TYPES. 
I. Mileage of each type of road. 
Data on productivity factors outlined above should correlate highly 
with average gross rents, but in correlating land value with these 
factors it would be necessary to add to the productivity factors 
data on average taxes per acre and the average mortgage rate of 
interest. 
Although complete information on all these factors is not available, 
the census does publish data which make possible the calculation 
of the following productivity factors by counties : 
1. Percentage of improved land. 
2. Percentage of woodland. 
3. Percentage of land needing drainage. 
4. Average yield per acre. 
This list, although not complete, furnishes a fairly good index of 
productivity, and the correlation of cash rent and land value with 
these factors will give a good measure of the accuracy of rent and 
value figures. 
Only the larger county groups were selected for this test. In the 
north groups 7, 10, 11, and 13 were used and groups 32, 33, 37, 41, 
42, 44, and 45 in the south. The southern groups were thrown to- 
gether and the correlation between average value and the produc- 
tivity factors determined. Then the correlations were determined 
for groups 37, 42, and 44 alone, thus eliminating all the southern 
groups except those including the major plantation areas. 
