40 BULLETIN 1300, U. S. DEPAKTMENT OF AGRICULTUBE 
of the amount of breeding. Indirectly it is determined at least 60 
per cent by the ratio of hog to corn prices in the preceding winter. 
As an indicator of the amount of breeding, it is very closely related 
to all other phases of the hog situation in the following two or three 
years. During the years studied, winter-pork production could have 
heen predicted with greater accuracy from knowledge of the summer 
live weight one and a half years before than from any knowledge of 
other phases of the hog situation dealt with here, or of corn crop or 
prices. 
The fluctuations in summer weight reveal a marked tendency for 
hog production to fall into a cycle of overproduction and underpro- 
duction, two years from one extreme to the other. The reason 
appears to be that the peak and low points in breeding come nearly 
a. year after the high or low hog-corn price ratios which warrant them. 
WESTER WEIGHT 
The correlations involving winter weight are in marked contrast to 
those involving summer weight. There is little relation between 
successive seasons. The reason is probably that, whereas fluctuations 
in summer weight depend largely on the proportion of old and young 
animals slaughtered, those in winter weight depend primarily On the 
degree of finish. The winter slaughter is more homogeneous in age 
than the summer slaughter. It is composed in the main of the large 
spring-pig crop, but the summer slaughter is composed of odds and 
ends, the relatively small fall-pig crop, old sows which have weaned 
their pigs and hogs slaughtered before Xovember or held until after 
February to take advantage of more favorable prices. The mini- 
mum price usually comes in December and the maximum in April or 
September, with relatively high prices throughout the summer season. 
As shown in Table 8 there are only a few correlations of any 
importance between winter weight and preceding conditions. The 
high correlations with the preceding corn crop ( + 0.64) and its price 
( — 0.64) presumably reflect the immediate effect of an abundance (or 
shortage) of corn on winter feeding. The correlation with the pre- 
ceding summer weight is probably due largely to the effect of spring 
breeding on the number of old sows slaughtered in both seasons. 
Many of the sows bred in the spring would not be slaughtered until 
after Xovember 1. Finally the negative correlation with the pre- 
ceding summer slaughter ( — 0.33) continuing through the winter 
( — 0.18) is due probably to the withdrawal of hogs from slaughter 
which, as we have seen, is the first effect of a big crop. 
Winter weight is determined 40 per cent by either the preceding 
corn crop or corn price (45 per cent by the two combined). Corn 
crop, summer weight, and summer slaughter combined determine 
59 per cent of its variation. The addition of other factors to this 
combination only increases it slightly. 
Summing up, winter weight is determined primarily by the supply 
of corn on hand and secondarily by the percentage of old sows in the 
winter slaughter as a result of heavy breeding the preceding spring. 
PRICE OF HOGS 
One naturally expects price to show a close negative correlation 
with supply. There is such a correlation in the case of hogs, but it is 
