24 
BULLETIN 1400, U. S. DEPARTMENT OF AGRICULTURE 
The number of cows and the dairy index together aeeounted foi 
55 per cent of all the variation in operator's earnings on the dairy 
farms, or for all but one-sixth of the variation in earnings on these 
farms that could be definitely assigned to any particular cause. 9 
The size of the dairy enterprise, and the efficiency with which it is 
conducted, are thus the principal factors which determine farm 
earnings on most farms in Chester County and should be given 
first consideration in trying to improve the business of any dairy 
farm in this region. 
Table 21. — Dairy farms, classified by number of cows and dairy index 
Dairy index, 1 
in dollars 
Number of farms with specified numbers of dairy cows 
5 to 10 
cows 
10 to 15 
cows 
15 to 20 
cows 
20 to 25 
cows 
25 to 30 
cows 
30 to 35 
cows 
35 to 40 
cows 
40 to 45 
cows 
45 to 50 
cows 
Total 
-50 to 
1 
8 
40 
20 
3 
2 
1 
to 50 
8 
32 
11 
2 
17 
48 
25 
2 
1 
4 
17 
9 
1 
2 
6 
3 
2 
1 
2 
"T 
40 
50 to 100 
1 
146 
100 to 150 
1 
150 to 200 
11 
200 to 250 
3 
Total 
53 
93 
74 
31 
13 
4 
1 
1 
270 
1 Value of milk and calves per cow less value of feed consumed, except pasturage. 
Table 22. 
■Average operator's earnings on dairy farms, with farms classified by 
number of cows and dairy index l 
Average operator's earnings on dairy farms 
with— 
Dairy index, in dollars 
5 to 10 
cows 
10 to 15 
cows 
15 to 20 
cows 
20 to 25 
cows 
25 to 30 
cows 
—50 to 
Dollars 
Dollars 
Dollars 
-1,700 
320 
970 
1,690 
2,870 
2,700 
Dollars 
Dollars 
to 50 
250 
590 
960 
1,200 
no 
800 
1,270 
2,150 
2,000 
1,280 
1,340 
1,680 
2,300 
300 
50tol00-.. . 
770 
100tol50-- 
1,730 
150 to 200- - 
3,750 
200 to 250 
i These two factors alone have a multiple correlation of iJ=0.73 with operator's earnings. The relations 
shown in this table are therefore significant. 
As is shown in Table 21, there was practically no relation between 
number of cows in the different herds and the efficiency with which 
the herd was operated. 10 
Table 22 shows the average operator's earnings in these different 
groups of farms. This table brings out strikingly the importance of 
the efficiency of operation of the dairy enterprise in determining the 
operator's earnings. For the farms with a dairy index below $50 
per cow, it made little difference whether there were 5 cows or 25 
cows in the herd; the earnings were uniformly low, with the excep- 
tion of a single group. Even with a dairy index between $50 and 
$100 per cow the earnings were only slightly larger for the large 
herds than for the smaller herds. But for herds above this point 
• The multiple correlation of these two factors alone with operator's earnings was i2=0.73. 
io The correlation is but r=0.11±0.04. 
