A Problem on Scale Criteria in Agricultural Sample Surveys
Masahiro Kobayashi
Ishikawa Agricultural College
Suematsu 1-308
Nonoichi, Ishikawa, 921-8836, Japan
kobayasi@ishikawa-c.ac.jp
1, On samples of rice cost production survey
The author pointed out some problems to pay attention to sample designs on surveys. To
illustrate by example, the author took the following survey of rice production costs in
Japan. Distribution and accumulation distribution of production costs are mentioned in the Report
on Production Cost of Rice, Wheat and Barley by AFF(Department of Agriculture and Forest,Fisheries).
Production cost of brown rice by years and agricultural regions are made at per 60kg and per 10a by
cost elements. Distributions of costs are made at 200yen intervals of total cost by numbers of farms,
production amount, planted area and sale amount. Population of the cost survey by the AFF is made
from the farms that sold more than 60kg of rice in a year. Specification of this population used on
findings of the Report on Rice selling amount of scales by the FA(Food Agency). The number of
farms in the cost survey as samples was settled according to the acreage under scales of planted area
by the FA report. In this survey, a stratified-two-stage-sampling method was used rationally in
consideration of agricultural areas and planted areas. Figure 1 illustrates the farm ratio (a) to
population according to the FA, and the survey of farm ratio (b), survey farm ratio to those that sold
rice (c) according to the AFF. We show 3 distributions conformable to survey needs.
Figure 1.Percentage of farms in the sample as related to size.
2, Gaps in sample and population
Using the result of the survey of rice production costs in 1992 and 93, relation of production cost
distribution and the characteristic of planted area as control variables is clear. The table is the result
35.00
30.00
%
25.00
20.00
15.00
10.00
5.00
0.00
-0.3
0.30.5
0.51.0
1.01.5
1.52.0
2.02.5
2.53.0
3.04.0
4.05.0
5.0-
10.0-
of the 1992 survey. It is the calculation of the ratio between surveyed farms as sample and as
population. In the table, (B) are production costs in yen per 60kg rice of every area (A) on the cost
survey. The descending order of costs is recognized. In other words, there is a merit of scale. As the
descending order becomes small, there is a complication at the stratum of farms of more than 7.0ha.
Segments of average production cost (C) are the intervals included among average production
costs (B) according to each planted area (A), counting from the bottom. For example, 23,677yen for
0.3-0.5 area is included in the interval of 23,500-25,300yen counting from the 23,500yen segment
that included 23,677yen. Other columns are counted in a similar way. Farm ratio (D) is the ratio of
Table. Comparison on ratios count and distributions.
(A)
Planted
area
(ha)
- 0.3
0.3- 0.5
0.5- 1.0
1.0- 1.5
1.5- 2.0
(B)
Production
cost (yen)
25,632
23,677
22,153
19,397
17,876
(C)
Segment
of
average
production cost
25,50023,500-25,300
22,100-23,300
19,300-21,900
17,700-19,100
(D)
Farm ratio to
total farms
20.17
24.62
30.89
11.64
5.33
(E)
Farm distribution
that is included in
(C)
24.20
10.70
7.12
19.23
10.21
1
(F)
Product amounts
ratio to total
farms
3.11
8.55
23.82
17.71
12.19
(G)
Product amounts
distribution that is
included in (C)
11.61
6.77
5.01
17.33
12.44
2.0- 3.0
3.0- 5.0
5.0- 7.0
7.0-10.0
10.0-
16,786
16,782
15,299
14,679
15,941
16,700-15,500
15,300-16,500
14,500-15,100
total
35.00
4.24
2.09
0.58
0.31
0.15
100.00
8.35
7.50
3.78
91.09
14.14
10.75
4.25
3.03
2.42
100.00
10.40
11.92
6.17
81.66
35.00
D
F
E
G
30.00
30.00
25.00
25.00
20.00
20.00
15.00
15.00
10.00
10.00
5.00
5.00
0.00
0.00
-0.3
0.3-0.5 0.5-1.0 1.0-1.5 1.5-2.0 2.0-3.0 3.0-5.0 5.0-7.0
7.010.0
10.0-
-0.3
0.3-0.5 0.5-1.0 1.0-1.5 1.5-2.0 2.0-3.0 3.0-5.0 5.0-7.0
7.010.0
10.0-
Figure 2. Comparison between farm ratios. Figure 3. Comparison between product amounts.
the number of farms as the population ratio. It is the distribution of the number of farms that are
counted according to planted area on the report by the FA. Product amount ratio on the farm
according to planted area (F) is the ratio of the number of farms which sold rice as a percentage of
total population, using the same report by the FA. Other columns are counted in a similar way.
Farm distribution (E) is the ratio of the number of farms as a sample ratio to the total farms
included in an interval of cost segment (C) counted from cost distribution in the Report by the AFF.
Product amount distribution (G) is the ratio of the number of farms that sold rice as a sample ratio
to the total farms included in the interval of cost segment (C) counted from cost distribution of
farms that sold rice in the Report by the AFF. The reason for the blanks in (E) and (G) is that from
the stratum of more than 3.0ha, cost slightly diminishes, and for more than 10.0ha, there is a cost
rise. Figure 2 is the illustration of (D) and (E), and figure 3 is the illustration of (F) and (G) in 1993.
We could to clarify the factors causing the difference between (D) and (E) in farm distribution,
and (F) and (G) in product amount distribution. The ascending order of the planted area of farms
does not correspond to a smooth descending order of production cost in distribution. This is the
most important factor that affected the concentration of distribution. In farms less than 1.5ha in Fig
2 and 3, we find a big difference of farm distribution in the population and in the sample. The
production cost of rice at every classification had a large variance, with a large concentration within
a limited distribution. In this range, it is difficult to definitely define the merits or to analyze
outcomes for farmers. Attention should also be paid to this situation in other economic surveys.
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