One reason for the difference between the total of the acreage equiva- 
lents in the tables and the over-all equivalent given in the Summary is 
that the separate equivalents cannot reflect the interaction between 
different causes of loss, that is, the effect that such causes have on 
each other. This may be illustrated by a hypothetical simplified example 
of an area in which 1,000 acres were devoted to cereal production. 
Assume that the actual harvest brought a return of $50,000 after 
estimated losses of $30,000 from diseases, $15,000 from insects, and 
$5,000 from weeds. If each is considered independently, the data may 
pe tabulated as follows, duplicated values being enclosed in parentheses: 
: Production 4 Losses 
: : $ : sAcreace tPer 
Cause of Loss ¢ frea : Value 3:Percentage:Value sEsuivalenteAcre 
: Acres : Dollars : Percent :Dellars ;: Azres :Dollars 
g : : $ ¢ 3 
Diseases 221/,000)/2250,000: 22 B7a5oe 385 30,5000e e375 30 
Insects eae 000):(50,000) : 123.2 ©: 15,000: ~ 231 ror ls 
Weeds : (1.000) : (504000) 3 9.1 : 5,099 ¢ o1 sks 
Sums ;_1,000 : 50,000) ti) See 350), 000) su eO9miassas5O 
The acreage equivalent in each case represents the number of acres that 
would not have been needed if the particular source of loss had not been 
present. That is, if only plant diseases could have been eliminated with= 
out affecting the other two causes of loss, 375 acres could have been 
saved, and the actual $50,000 return could have been expected as the in- 
come from the remaining 625 acres, 
The sum of the three equivalents is 697 acres if they are considered 
independently. 
However, if no disease was to be anticipated and only 625 acres had 
been planted to the disease-free crop, insect damage, at $15.00 per 
acre, would have amounted to only $9,375 instead of the $15,000 shown 
in the table. The potential return would have been $59,375 (that is, 
$50,000 plus $9,375), and the insect loss percentage would have been 
15.79 percent. This gives an acreage equivalent of 98.68 acres (that 
is, 15.79 percent of 625 acres). 
Reducing the acreage by another 98,68 leaves 526.32 acres as all that 
would have been needed if both diseases and insects had been avoided, 
At $5.00 per acre, the loss from weeds on this reduced acreage would 
have amounted to $2,631.60. This gives a loss percentage of 5.0 percent 
(that is, $2,631.60 + $52,631.60). The acreage equivalent would be 
26.32 acres. 
The total acreage equivalent, allowing for interaction, would thus be 
375 + 98.68 + 26,32 = 500 acres, 
= 10 = 
