Overview of Sample Surveys for
Forecasting & Estimating U.S. Crops
presented by
Theresa “Terry” Holland
National Agricultural Statistics Service
U.S. Department of Agriculture
Regional Workshop on
Sampling for Agricultural Surveys
23 June 2011
Montevideo, Uruguay
NASS Data Series for U.S. Crops
Crop Progress & Condition
Area
planted & harvested
Production
Stocks
Prices Received by Farmers
Monthly Marketings
Values
U.S. Crop Standards
standard weight
standard
moisture
standard
price
marketing year
starts:
Wheat
60 lb (27.2 kg) per bushel
13.5%
$/bu
June 1
Barley
48 lb (21.8 kg) per bushel
14.5%
$/bu
June 1
Oats
32 lb (14.5 kg) per bushel
14.0%
$/bu
June 1
Flaxseed
56 lb (25.4 kg) per bushel
8.0%
$/bu
June 1
Cotton
480 lb (217.4 kg) per bale
$/lb
August 1
Rice
100 lb (45.3 kg) per hundredweight
$/cwt
August 1
Corn
56 lb (25.4 kg) per bushel
15.5%
$/bu
September 1
Sorghum
56 lb (25.4 kg) per bushel
14.0%
$/cwt
September 1
Soybeans
60 lb (27.2 kg) per bushel
14.0%
$/bu
September 1
8.0%
$/cwt
September 1
Sunflowers
100 lb (45.3 kg) per hundredweight
System of Crop Forecasts & Estimates
early season
area/trees planted
area/trees expected for harvest
during season
yield forecasts
end of season
area/trees harvested
total production
end of marketing year
revised total production
Possible Methods for Crop Forecasting & Estimation
growers’ actual data
area/trees planted/harvested
quantities harvested/sold/stored
growers’ expectations
areas expected to be planted/harvested
expected yields
objective counts & measurements
plant/fruit counts & measurements
expert opinion
crop progress
growing conditions
remote sensing
NASS Survey Program for Major Crops
jan
feb
mar
apr may
jun
jul
aug
sep
oct
nov
dec
small grains
Crop Yield Surveys
summer crops
Quarterly Agricultural Surveys
summer crops:
planting intentions
planted area
harvest intentions
–
small grains:
planted area
harvest intentions
planted area
harvest intentions
planted area
harvested area
production
(for harvest next year)
on-farm grain stocks:
storage capacity
quantity stored
storage capacity
quantity stored
storage capacity
quantity stored
storage capacity
quantity stored
Off-farm Grain Stocks Surveys
Prices Received by Farmers
small grains - final old crop summer crops - final old crop
planted area
harvested area
production
planted area
Quarterly Agricultural Surveys
sample:
based on –
total cropland
areas of specific crops
grain storage capacity
data obtained:
areas
intended vs. actual
planted vs. harvested
production
grain stored on farm
data collection modes:
mail questionnaire
Internet questionnaire
telephone/CATI interview
personal interview
Crop Acreage, Yield & Production
production
area
Quarterly
Agricultural
Surveys
x
yield
Agricultural Yield
Surveys
Objective Yield
Surveys
Quarterly
Agricultural
Surveys
Crop Yield Surveys
Agricultural Yield
Objective Yield
samples:
March & June Ag Surveys
March & June Ag Surveys
crops of interest
rotated out reps
exclude high strata
exclude NOL
crops of interest
supplemental
Crop Yield Surveys
Agricultural Yield
Objective Yield
commodities surveyed:
small grains
small grains
barley
oats
winter wheat
durum wheat
other spring wheat
winter wheat
summer crops
summer crops
corn
cotton
dry beans
hay
peanuts
rice
tobacco
sorghum
soybeans
sugarcane
sunflowers
canola
corn
cotton
soybeans
potatoes
Crop Yield Surveys
Agricultural Yield
Objective Yield
data obtained:
farmer reported yields
yields based on
field counts & measurements
area updates
area updates
data collection modes:
mail questionnaire
Internet questionnaire
telephone/CATI interview
personal interview
field visit
personal interview
Crop Yield Surveys
Agricultural Yield
Objective Yield
advantage:
inexpensive
objective
disadvantage:
subjective
expensive
Crop Yield Surveys
small grains: May thru September
summer crops: August thru November
25
yields to reflect conditions
as of 1st of month
1
data collection starts
25th of previous month
Objective Yield Sample Sizes
number of
States
% of
U.S. crop
sample
size
Wheat
10
53%
1410
Corn
10
84%
1920
Soybeans
11
84%
1835
Cotton
6
75%
1227
Potatoes
7
75%
1290
updated 2010
Objective Yield Sample Sizes
WHEAT n=1410
10 states average 67% of U.S. winter wheat production
winter wheat in the 10 states averages 50% of U.S. production of all wheat
160
100
110
130
80
280
180
210
80
80
Objective Yield Sample Sizes
CORN n=1920
10 states average 84% of U.S. corn production
180
150
260
150
150
290
280 170 140
150
Objective Yield Sample Sizes
SOYBEANS n=1835
11 states average 84% of U.S. soybean production
120
120
140
120
210
230 180
130
150
285
150
Objective Yield Sample Sizes
COTTON n=1227
6 states average 75% of U.S. upland cotton production
upland cotton in the 6 states averages 65% of U.S. production of all cotton
150
112
150
525
110
180
Objective Yield Sample Sizes
POTATOES n=1290
7 states average 83% of U.S. fall potato production
fall potatoes in the 7 states average 75% of U.S. production of all potatoes
160
200
175
150
300
155
150
Objective Yield Sampling
Fields are selected
based on area
expected for harvest.
Objective Yield Sampling
crop
acres
expansion factor
expanded crop
acres
cumulative
expanded crop
acres
segment
tract
field
selected acres
4087
6
1
130.0
53.000
6890.00
6890.00
1306.11
5030
1
2
69.0
53.000
3657.00
10547.00
10269.71
5030
1
5
59.0
53.000
3127.00
139674.00
6049
3
2
17.0
53.000
901.00
14575.00
6049
3
4
62.0
53.000
3286.00
17861.00
5031
2
2
33.0
53.000
1749.00
19610.00
6145
2
3
34.0
53.000
1802.00
21412.00
6145
2
5
48.5
53.000
2570.50
23982.50
4381
1
2
65.0
194.000
12610.00
36592.50
21896.91
5391
1
3
78.0
194.000
15132.00
51724.50
37160.51
4476
4
1
105.0
106.143
11145.01
62869.51
55087.71
4485
1
2
80.0
106.143
8491.44
71360.95
64051.31
4485
1
4
100.0
106.143
10614.30
81975.25
73014.91
4494
5
1
87.0
106.143
9234.44
91209.69
81978.51
4494
5
2
48.0
106.143
5094.86
96304.55
4494
5
3
85.0
106.143
9022.15
105326.70
99905.71
4494
5
4
100.0
106.143
10614.30
115941.00
108869.31
6467
4
6
32.0
⋮
9.0
106.143
⋮
53.000
3396.58
⋮
477.00
119337.58
⋮
895617.99
117832.91
⋮
4153
1
⋮
1
4153
1
7
14.0
53.000
742.00
896359.99
19233.31
interval = total expanded acres/sample size = 896359.99/100 = 8963.60
random start ∊ (0. interval] = 1306.11
46124.11
90942.11
Objective Yield Sampling
starting corner
Plot 1
Plot 2
Samples consist of 2 plots
randomly located within each selected field.
Objective Yield Sampling
5-ft buffer zone
count area
Each plot consists of a 5-foot buffer & a count area.
count area
Wheat
Corn
Cotton
Soybeans
Potatoes
3 rows
2 rows
2 rows
2 rows
1 row
x
x
x
x
x
21.6 inches
15 feet
10 feet
3.5 feet
20 feet
Yield Components
number of fruit
per acre
x
gross yield
weight
per fruit
–
harvest loss
per acre
Gross Yield Components
WHEAT
at harvest:
forecast:
heads per acre
grain weight per head
heads
grain weight
moisture content
stalks
heads in boot
emerged heads
historical average
fertile spikelets
grains per head
head weight
Gross Yield Components
CORN
at harvest:
forecast:
ears per acre
grain weight per ear
ears
grain weight
moisture content
stalks
ears & ear shoots
ears with kernels
historical average
kernel row length
ear diameter
ear weight
Gross Yield Components
SOYBEANS
at harvest:
forecast:
plants per acre x pods per plant
bean weight per pod
plants
pods
bean weight
moisture content
plants
main stem nodes
lateral branches
blooms, dried flowers & pods
pods with beans
historical average
lateral branches
pods with beans
pod weight
Gross Yield Components
COTTON
at harvest:
forecast:
bolls per acre
lint weight per boll
open bolls
large bolls
lint weight
moisture content
squares
blooms
bolls
burrs
historical average
blooms
bolls
large boll weight
Gross Yield Components
POTATOES
at harvest:
forecast:
hills per acre
potato weight per hill
hills
potato weight
—
—
Harvest Loss Component
gross yield
–
harvest loss
after harvest:
gleanings
forecast:
historical
average
Forecasting the future
is dependent on
patterns of the past...
Objective Yield Forecasting
Current Counts
& Measurements
Historical Data Models
Counts & Measurements ⇒ Final Yield
Forecast
Objective Yield Model #1
Number of Fruit
final fruit count
1200
1000
800
600
400
200
0
0
200
400
600
800
1000
1200
early season variable
Weight per Fruit
1.2
final weight
1.0
0.8
0.6
0.4
0.2
0.0
0
5
10
15
20
25
30
early season variable
35
40
45
50
Objective Yield Model #2
Early Season Yield Forecast
150
07
140
05
NASS yield
130
00
99
98
120
95
97
110
y = 0.0013x - 76.025
09
03
02
08
04
06
100
90
96
80
120000
01
130000
140000
150000
independent variable
160000
170000
Yield Survey Indications
Objective Yield 1:
➀ regress sample level counts &/or measurements to final crop-cutting data
➁ forecast yields for each sample
➂ average sample level yields to state & regional forecasts
overestimates
Objective Yield 2:
➀ aggregate sample counts &/or measurements to state & region – independent
variable
➁ regress independent variable to final NASS yield
unbiased estimates
Agricultural Yield:
➀ summarize grower reported yields using sampling weights
underestimates
Yield Forecasting Process
➊ regress Objective Yield1 & Agricultural Yield indications to final NASS yield
➋ determine prediction intervals for each regression (± 1 SE)
➌ determine the overlap of the three prediction intervals
170
160
150
140
130
120
110
OY 1
OY 2
AY
overlap
➍ use expert knowledge to decide where within the overlap interval
to set forecast
Analyzing Yield Data
survey data
•
•
•
•
impact of unusual reports
maturity stages
yield components
other data relationships
crop progress reports
• planting dates
• pollination dates
weather data
• rainfall
• heat degree days
industry contacts
• insect problems
• disease problems
Reliability of U.S. Crop Production Forecasts
Reliability of U.S. Crop Production Forecasts
Grain & Oilseed Stocks Surveys
Off-farm
On-farm
sample:
commercial
grain storage operations
elevators
warehouses
terminals
grain & oilseed processing plants
other storage facilities not classified as farms
farms in Agricultural Surveys
Grain & Oilseed Stocks Surveys
Off-farm
On-farm
data obtained:
all whole (unprocessed) grains & oilseeds
on hand or stored in permanent or temporary facilities
regardless of ownership or intended use
data collection modes:
mail questionnaire
Internet questionnaire
telephone interview
personal interview
mail questionnaire
Internet questionnaire
telephone/CATI interview
personal interview
Grain & Oilseed Prices Surveys
sample:
firms that purchase whole grains & oilseeds from farmers
30 States in monthly program account for 90% of all U.S. sales
data obtained:
quantity purchased from farmers during previous month
total dollars paid for this quantity
including quality discounts & premiums,
excluding deductions for drying, handling, cleaning, storage, grading, checkoff fees, etc.
data collection modes:
mail questionnaire
Internet questionnaire
telephone interview
personal interview
Crop Progress & Condition Surveys
monthly Crop Production reports
issued on or about 10th day of each month
reflect conditions as of 1st day of month
weekly Crop Progress & Condition reports
issued 1st business day of each week, April-November
reflect status & conditions as of previous Sunday
farmer activities, such as planting and harvesting
progress of crops through various phenological stages of development
crop, pasture & range conditions
soil moisture ratings
Crop Progress & Condition Coverage
Crop progress & condition:
barley, corn, cotton, peanuts, oats, rice,
sorghum, soybeans, sugarbeets, sunflowers,
winter wheat, spring wheat
States that account for
at least 75% of area
planted to crop of interest
Pasture & range condition:
all States except Alaska & Hawaii
Soil moisture &
days suitable for field work:
all States except Alaska, Arizona,
California, Hawaii & Nevada
Narrative:
all States
At least one reporter for each agricultural county in each State
Corn Progress & Condition
18 states account for 92% of acres planted to corn in 2009
planted
emerged
silk
dough
dent
mature
harvested
condition
Soybean Progress & Condition
18 states account for 95% of acres planted to soybeans in 2009
planted
emerged
bloom
set pods
drop leaves
harvested
condition
Winter Wheat Progress & Condition
18 states account for 89% of acres planted to winter wheat for 2010
planted
emerged
headed
harvested
condition
Spring Wheat Progress & Condition
6 states account for 99% of acres planted to spring wheat in 2009
planted
emerged
headed
harvested
condition
Cotton Progress & Condition
15 states account for 99% of acres planted to cotton in 2009
planted
squaring
set bolls
bolls open
harvested
condition
Other Crops Progress & Condition
number
of
States
% of
2009
planted
area
progress stages
Barley
5
81% planted, emerged, headed, harvested, condition
Oats
9
64% planted, emerged, headed, harvested, condition
Peanuts
8
98% planted, pegging, harvested
Rice
6
100% planted, emerged, headed, harvested, condition
Sorghum 11
98% planted, headed, coloring, mature, harvested, condition
Sugarbeets
4
84% planted, harvested
Sunflowers
4
85% planted, harvested
Crop Progress & Condition Reporters
5,000 reporters
whose occupations provide frequent opportunities
to observe crops and/or contact farmers in their counties
Extension Service agents
USDA Farm Service Agency directors
NASDA enumerators
Agribusiness representatives
Crop advisors
Farmers
Crop Progress & Condition Data Collection
mail
phone
fax
personal interview
e-mail
Internet
~ 80-85% ~
Crop Progress & Condition Questionnaire
Required items specified weekly by HQ
historical trends at national level
current trends at national level
“rules”
States may deviate from requirements
start earlier or end later for particular items
additional items of interest to State
All questions must use standardized wording!
Crop Progress & Condition Summary & Analysis
• County averages weighted by planted areas
to State-level estimates
• State estimates weighted by planted areas
to U.S. estimates
• State & U.S. progress estimates compared with
last week, last year and 5-year average
• within-season progress cannot go backwards
• unusually large or small changes must be explained
Crop Progress & Condition Reports
issued at 12:00 Eastern
2nd business day of week
issued by World Agriculture Outlook Board
afternoon 2st business day of week
issued at 16:00 Eastern
1st business day of week
Crop Progress & Condition Uses & Users
producers
agribusinesses
commodities traders
government agencies
researchers
assess current growing conditions
in order to reduce inherent risks of doing business
planning, decision-making, research
NASS
interpretation of survey results for crop yield forecasts