Upload
dinhdang
View
237
Download
0
Embed Size (px)
Citation preview
1
Improved Methodology for
Estimation of Food Stocks
Philip Abbott
Purdue University
Joint National Workshop on Rice Data for Thailand and
the Philippines
Sukosol Bangkok Hotel, 16-17 December 2013, Bangkok, Thailand
Guidelines for Improved Stocks data
� 2007-08 Food Crisis � Need for better agricultural commodity market information (G8/G20, UNHLTF, International organizations)
� AMIS: Agricultural Market Information System
� Gates Foundation- Bangladesh, India, Nigeria
� Japan project – Thailand, Philippines
� Information on grain and oilseed stocks emerged as a key inadequacy to be addressed
� Annotated outline for Guidelines
� Best practices from literature review
� Issues and recommendations for stocks data
collection
2
Why is better stocks data needed?
� Market performance
� Annual carry-out stocks as a determinant of private
market prices
� Policy implementation
� Policy induced disequilibrium resolved by stocks
accumulation or release
� Food security
� Indicator of national availability
� Food aid supplies
� Economic agents, public and private, hold stocks for food security or business objectives
Why agents (farmers, traders, livestock producers,
food processors, etc.) hold stocks
� Local/household food security
� Regional trade and domestic seasonal pricing
� International trade
� Supplies for public distribution and food aid
� Working inventories for livestock producers
and food processors
� Consequence of policy implementation --
incentives to store
3
Definitional Issues� Public versus private stocks
� Public stocks may have specific purposes – emergency
reserves, strategic reserves
� Even with public stockpiling, farmers and traders may
hold significant stocks
� Working (pipeline) stocks versus buffer stocks
� Distinction ambiguous to private agents holding stocks
� Annual carry out stocks
� Stocks held when new harvest begins
� Food security across crop years/seasons
� Price stability – stocks link prices across years
Current and Best Practices
� Developed country ag exporters run quarterly
surveys –� US (USDA, NASS), Canada (Statistics Canada)
� Brazil and Australia have run incomplete surveys
� Developing countries – only Philippines to our
knowledge surveys stockholders (monthly)
� FAOSTAT, USDA PS&D, AMIS and most
national governments must rely on estimating
stocks as a residual from food balance or
supply-utilization equilibrium
4
Stocks as a residual?� Food balance:
Carry-in stocks + production + imports
= food use + feed use + industrial use, waste, losses and
seed use + exports + carry-out stocks
� Problems with this approach:
� Uses unknown – cannot solve for two unknowns from
one equation
� Both use and stocks are unknown in this equilibrium
� Stocks may be easier to observe than use
� Errors in production, trade, use magnified
� Stocks data a check on availability data
� Seed, waste, loss shares may change over time
Stocks estimate vary widely, but are converging where surveyed
Thailand Philippines
5
Where stocks data are reliable (U.S.), they play a
role in private price determination
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0 50 100 150 200 250 300 350
Corn
Corn
0.00
0.05
0.10
0.15
0.20
0.25
0 100 200 300 400 500 600
Soybeans
Soybeans
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0 100 200 300 400 500
Wheat
Wheat
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0 200 400 600 800 1000 1200
Rice
Rice
Fundamental Recommendations
� Better stocks data requires more data
collection!
� If stocks are not surveyed, use should be
� Surveys are needed, separately for both on-
farm and commercial stocks
� Guidelines are developed here to better
estimate stocks based on surveys
� Following observed “best practice” cases
6
Guidelines – Annotated Outline
� Introduction/Background – Why measure stocks?
� Overall recommendations - Surveys
� What to measure
� When and how often to measure
� Identifying relevant agents for surveys
� Collection methods and logistics
� Sample strategy and design
� Questionnaires
� Documentation
� Results reporting
Introduction/Background – Why
measure stocks?
� Motivate why stocks data should be
collected, based on data needs of both policymakers and market participants
� Food security policy
� Market (agricultural policy) interventions
� Market performance
� Clarify relevant definitions
� Annual carry-out stocks are the focus here
7
Overall recommendations� Issues
� Residual approach not well identified – multiple unknowns
� Residual only identifies changes in stocks
� Errors, unknowns in other components of food balance
� Surveying is costly
� Questions raise sensitivity. Answers may be unreliable
� Who to survey? Public, on-farm and commercial stocks
� Recommendations
� Surveys are preferred to estimating stocks as a residual in food balance equilibrium.
� Both on-farm and commercial surveys should be conducted, separately
� Public stocks reported - detail maintained in stocks composition
� Levels, not just changes reported
� Inconsistencies should trigger improvements in surveying procedures rather than ad hoc data adjustments
� Fallback:
� If stocks surveys of private agents (farmers and commercial storage) are not conducted, the empirical foundations of the residual estimation strategy need to be substantially strengthened.
What to measure � Annual carry-out stocks the objective
� Quantity of a commodity in storage at the specific point in the
crop year when stocks are at their lowest level, coinciding with
the first day of the month when harvest begins.
� Other definitions typically apply to purposes of public stocks
� Ambiguities mean it may be difficult or impossible to identify
which subcategory of stocks (e.g. working stocks or buffer stocks)
a particular stock of grain is held
� Grain, milled rice, processed products reported as grain equivalent (e.g. milled rice equivalent)
� Focus on grains and oilseeds a fallback
� Non-tradeables?
� AMIS a response to inadequate world market information, but
� Where this is an issue (Africa) non-tradeables matter to
consumption substitution
8
When and how often to measure � Issues
� Should survey be conducted more than once per year?
� Best practice cases are quarterly, monthly
� Crop year and seasons properly defined
� Calendar year data only if that is a reasonable crop year
� Recommendation
� Surveys should be conducted at the beginning of each crop
year/ season (when harvest begins)
� Stocks surveys need to be done over a few days after the target
date of the survey. This implies use of a short, focused
questionnaire
� Fallback
� More frequent surveying than once per year is desirable, but
monthly surveys not required
Identifying relevant agents for surveys� Issues:
� Agents may include – traders, commercial storage
operators, and end users (food processors, livestock
feeders, etc.)
� Area or list frame? Lists of whom?
� Maintaining lists – e.g. firm entry and exit
� Recommendations
� Lists to insure nationally representative sample
� Agricultural or rural census (household surveys)
� “Census” of Commercial storage operators
� Public records, regulatory filings only starting point,
agency responsible for list maintenance
9
Collection methods and logistics� Online (web/email), mail (postal service), telephone,
or interview?
� Online most cost effective, but
� Online response rates low even in developed countries
� Infrastructure for online, telephone and even mail may be
inadequate, so that interviewing is very likely to be required
� Online methods may “leapfrog” mail in developing countries
� Recommendations
� Sequential collection from least to most costly method, as
followed now in best practice cases
� Separate on farm and commercial surveys
� Commercial survey under authority of regulatory agency
� Statistical agencies have experience with surveying
� Methods may differ by agent
Sample strategy and design� Issues for nationally representative samples
� Stratification strategy
� Regional information?
� Storage may occur where crop not grown
� Non-farm households?
� Farms that do not generate marketed surplus?
� Recommendations
� Complete enumeration of large commercial storage entities
and large farms
� Samples of smaller entities
� Models to estimate data when samples taken for smaller agents,
missing observations
� Include samples of agents who hold stocks, whether for food
security or market performance
10
Questionnaires� Issues
� Comprehensive survey or target stocks positions?
� In what units of measure? Local or standard?
� Ownership status
� Storage capacity
� Sensitivity: Will farmers or traders reveal stocks information
accurately?
� Recommendations
� Simple questions focusing on stocks on hand at the time
interview is conducted (or report is provided via phone, web or
mail).
� Integrate with limited production survey, not comprehensive
rural household survey
� Learn from experience how to address sensitivities
Documentation, Results reporting
� Even in the “best practices” cases public, thorough
documentation of methods to estimate stocks data were
not publicly available.
� Results now are quickly reported, in detail.
� Recommendations
� Publicly available and complete documentation, including
sampling strategy, survey coverage, questionnaires, timing, and
adjustments/procedures to move from sample results to
population predictions is needed
� For stocks estimates to be useful, reports must be issued quickly
after surveys (less than one month). They should include detail
(public, commercial, on-farm; regional data; etc).
11
Fallbacks if Stocks Surveys are not
Implemented
� Fallbacks
� Only commercial storage survey, not on-farm
� Survey use more frequently – at least once per year (food
consumption, feed use, industrial)
� Better empirical basis for “rules of thumb” on seed, waste,
even consumption
� Enhance expertise for in-country analysts who must estimate
food balance
� There are not “best practice” methodologies that extract
better information from non-existent data
� Collecting stocks data may be most cost-effective alternative
Conclusions� Better market information requires better data
collection
� Annual carry-out stocks information important to market performance, policy implementation and food security
� Estimating stocks as a residual in food balance is not a
well identified strategy, likely to lead to errors
� Best practices cases use targeted surveys that
separately measure on-farm and commercial storage
� Cost and sensitivity are limiting factors, but empirical basis for
residual approach requires better data as well, and collecting
stocks data is seen there as most cost-effective
� Fallbacks may result in less ambitious surveys than in current
best practice cases
12
Appendices
Data for Thailand and the Philippines
Questions related to surveying stocks in Thailand
Thailand – S&U data comparisons
10
12
14
16
18
20
22
24
26
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
Milled Production
AMIS USDA FAO National
-6
-5
-4
-3
-2
-1
0
1
2
3
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
Stock Variation
AMIS USDA FAO National
0
2
4
6
8
10
12
14
16
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
Domestic Use
AMIS USDA FAO National
0
2
4
6
8
10
12
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
Exports
AMIS USDA FAO National
13
Thailand – Stocks data comparisons
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
S/U Based on Total
AMIS USDA FAO Nat ional
0
5
10
15
20
25
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
Ending stocks
AMIS USDA FAO National
Thailand – Food balance and price data comparisons
14
Philippines – S&U data comparisons
0.00
0
2
4
6
8
10
12
14
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
Milled Production
AMIS USDA FAO National
-1.5
-1
-0.5
0
0.5
1
1.5
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
Stock Variation
AMIS USDA FAO National
0
2
4
6
8
10
12
14
16
18
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
Domestic Use
AMIS USDA FAO National
0
0.5
1
1.5
2
2.5
3
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
Imports
AMIS USDA FAO National
Philippines – Stocks data comparisons
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
S/U Based on Use
AMIS USDA FAO National
0
2
4
6
8
10
12
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
Ending stocks
AMIS USDA FAO National
15
Philippines – Food balance and price data
comparisons
Questions related to surveying stocks in
Thailand --Basics� What commodity – Rice
� Which stocks definition?
� Private annual carry-out stocks? Seasonal stocks for multiple crops?
� When to measure stocks?
� Is calendar year the best designation of crop year?
� What is the seasonal pattern of production? How do seasons contribute to variability?
� Is seasonal carry-out useful? Discussed in the Thai market?
� Units of measure? Metric tons, kilograms?
� Questionnaires
� How to ask about stocks to avoid sensitivity?
� Is capacity relevant to agent stockholding?
� Are there any public stocks?
� Do policies induce stockholding?
16
Questions related to surveying stocks in Thailand
� Has there been any debate on collecting
stocks data for Thailand?
� Why are data not collected? Expense? Sensitivity
of questions, hence unreliable responses?
� Are food balance estimates generated by the
government? By whom? Are stocks estimated as
a residual?
� Are use estimates made by the Thai government?
How?
� Are exports reported to the government?
Questions related to surveying stocks in Thailand
� Has there been supply chain research to identify actors in rice market, estimating their role, size, etc.?
� Who is believed to hold rice stocks in Thailand? How much do they hold after good years?
� What collection methods are necessary for each agent?
� Farmers must be interviewed? Now done that way for
production survey?
� Might commercial agents reply to internet based
options?
17
Relevant agents?
� Subsistence farmers (% of farmers?)
� Commercial farmers
� Small traders (number, % of stocks? Of transactions?)
� Large traders (number, size cut-off, % of stocks?)
� Exporting agents? (number, size cut-off, % of stocks?)
� Transporting agents
� Retail agents (supermarkets, shops)
� Consuming households
� Food processors?
� Feed use/ livestock producers?
Questions related to surveying stocks in Thailand
� Is there private information on the rice
supply chain?
� Do traders or exporters register with government?
Are they regulated? How?
� Are there trade associations? Do they collect data
from members?
� Are exports reported to the government?
� Are differences in export data now due to timing?
18
Questions related to surveying stocks in Thailand
� Can the crop cutting (rice production) survey
be expanded to include stocks questions?
� When in relation to harvests is the survey taken?
Is timing useful for stocks estimation?
� Is the sample based on an agricultural census
(conducted how often)? Who is surveyed?
� Are there other questions beyond area, yield
and/or production?