14 BULLETIN 923, IT. S. DEPARTMENT OF AGRICULTURE. 
practiced in this section where many cows freshened in the spring 
and where a large amount of good pasture furnished an abundance 
of feed for " summer dairying." Although they may approximate 
the relationship found in near-by sections, they can not be applied to 
all sections of the United States. 
DETERMINATION OF THE BULK LINE OF PRODUCTION. 
When it is required to fix a price to represent the cost of produc- 
ing milk for any section or group of dairymen, it is evident that if 
the actual average cost is used for this purpose then one-half of the 
milk is produced at a cost greater than the sum fixed. Therefore, if 
the price of milk is based on the average cost of production it would 
tend to discourage production and decrease the supply. On the 
other hand, the least economical producers should have little influ- 
ence in determining the cost of production for any group of dairy- 
men. 
There is a line on the scale of costs, however, below which the 
greater quantity of the milk is produced. This line, called the bulk 
line, is placed where it will usually include from 80 to 90 per cent 
of the volume of milk produced. It is aimed to cover the cost of 
producing all milk except that produced at extremely high costs. 
Some of the factors to take into consideration in locating the bulk 
line are illustrated in figures 1 and 2. Attention is called to the 
fact that the higher the cost the less the volume of milk produced. 
The horizontal lines which indicate volume of milk are long in the 
middle of the group and the vertical lines are short, but as the cost 
of production increases the vertical lines rapidly increase in length. 
As regards the placing of the bulk line in connection with the 
volume of milk produced in the present investigation, the line for 
the summer of 1917 might have been located in figure 1 at the point 
A, or possibly at C, but hardly at E, because the rapid increase in 
cost, as shown by the length of the line CD, is not compensated for 
by the extra volume of milk (line DE) produced at the high cost. 
Similarly the line for the summer of 1918 would not be placed higher 
than F. The bulk line for the winter production of 1916-17 (fig. 2) 
might be placed at either A or B, and that for the winter of 1917-18 
atC. 
MONTHLY DISTRIBUTION OF FACTORS IN MILK PRODUCTION. 
The lower net feed cost for November as compared with October in 
Table 14 is due to the larger credit for the amount of manure voided 
in the barn. The gross feed and bedding cost is a more accurate 
index of the relationship of the cost of feed in October and 
November. 
It will be noted that during the first year the income from milk 
during each season corresponded very closely to the volume of milk 
