RELIABILITY AND ADEQUACY OF FARM-PRICE DATA 11 
of the month were obtained from crop reporters, the prices of crops 
were weighted by counties within the State, and the census acreage 
was used as a basis of weighting. 
The prices of minor crops, of livestock, and of livestock products 
are averaged for the State — a straight average — the only weighting 
being whatever may result from having more reports from those 
parts of the State in which the sales of any particular product are 
most numerous. 
UNITED STATES MONTHLY AND ANNUAL PRICES 
In combining the farm prices for all States into a United States 
monthly farm price for each product, as released each month by 
the department, the State prices have been weighted according to 
the latest estimate of the production of each crop, in the case of 
crops, and according to the number of head of each class of live- 
stock on farms January 1, in the case of livestock. Census produc- 
tion weights are used for livestock products and for such other 
products as can not be weighted as indicated above. 
With crops, the December estimates of production by States are 
used as weights as soon after the estimates are made as possible, 
usually with the January prices. Since the December 1 prices are 
used in determining the December value of crop production by 
States and for the United States, the average value per unit of the 
United States production of a given crop is also the United States 
average price for December 1. The December estimates of produc- 
tion are used as " constant " weights for the ensuing year until the 
December estimates are again available unless there has been a 
marked shift in production, in which case a change in weights to 
the current year's estimated production is made at or about harvest 
time. When the January 1 estimates of livestock are used as weights, 
the new weights are used each year with the February monthly 
prices, as well as with the January 1 values of livestock per head. 
This method lends itself readily to determining an average price 
for the United States each month as the prices become available. 
It has the disadvantage of giving a State the same weight each 
month of the year whether there are many sales during that month 
or only a few. In case no prices are reported from a given State 
in any particular month, only the prices and weights of the States 
reporting are used in determining the United States average. 
The annual crop-year or calendar-year average price for the 
United States 4 is determined by weighting these monthly prices for 
the United States on the basis of the relative quantity of the crop 
usually marketed each month. 
Farm prices are more like index numbers than like actual prices. 
When weights are used the price each month within the State is 
weighted by constant weights based on the acreage in the different 
crop-reporting districts within the State, The United States 
monthly prices within the year are weighted by constant weights 
based on the annual production of the different States, which change 
4 A price summary for the year with crop-year average prices for the United States 
since the monthly-price series began is published each year in the December issue of 
" Crops and Markets," for crops, and in the February issue for livestock and livestock 
products^. Previous to 1827 these monthly issues were called " Supplements." 
