Trout Production Methodology and Quality Measures

Trout Production Methodology and
Quality Measures
ISSN: 2326-0394

Released March 6, 2014, by the National Agricultural Statistics Service (NASS), Agricultural Statistics Board, United States Department of
Agriculture (USDA).

Annual Trout Production Survey Methodology
Scope and Purpose: A Trout Production Survey is conducted annually, which includes all states with known trout
operations. Data are collected on number of operations, annual production, value of sales, value of distributed fish, and
point of first sale and losses.
Data collected on number of operations, annual production, value of sales, value of distributed fish, and point of first sale
and losses are published for 16 states. The publication contains estimates for nine other states, which are combined into an
“Other States” category. After each Census of Agriculture, which is an exhaustive data collection effort for all known
agricultural operations across the United States, the list of published states is evaluated and modified to include the largest
trout producing states.
Survey Timeline: Data are collected for the previous year’s production beginning in January. States complete data
collection, analysis, summarization, and submission of estimates over approximately a six-week period ending in early
February. The following week, a national review is completed and national estimates are established. Estimates are
released to the public at 3:00 p.m. ET in late February on the date designated by the Agricultural Statistics Board on its
annual publications calendar.
Sampling: The target population for the Trout Production Survey is all trout farming operations that sell fish or have the
potential to sell fish in the selected states. A state is included for the Trout Production Survey if it produces at least 1% of
the total production for the United States. All records on the National Agricultural Statistics Service (NASS) List Frame
with positively reported trout data from a past survey are sampled. The List Frame is a current and unduplicated list of
agricultural operations, and all current trout operations are assumed to be on the list. If a new trout operation is found at
any time, the operation is added to the List Frame. All trout operations are sampled and have a weight equal to one. Each
respondent operation accounts only for itself. The NASS Area Frame, which is a sampling frame of all land area, is not
constructed nor sampled to identify trout operations, so there is no area frame component to the annual Trout Production
Survey.
Data Collection: State statisticians are responsible for coordinating their own data collection strategy for their respective
state. Data are collected by mail, telephone, Electronic Data Reporting (EDR), Computer Assisted Personal Interviewing
(CAPI), and personal interviews. For EDR, a questionnaire is enclosed with a letter for the respondent to complete and
return by mail. The questionnaire also provides a survey code that can be used to complete the survey securely online. If
response is not received by mail or the Internet, respondents are contacted by phone for the survey data. Personal
interviews are usually reserved for large operations or those with special handling arrangements.
Survey Edit: As survey data are collected and captured, data are edited for consistency and reasonableness using
automated systems. Reported data are edited as a batch of data when first captured. The edit logic ensures administrative
coding follows the methodological rules associated with the survey design. Relationships between data items (i.e.
responses to individual questions) on the current survey are verified. Some data items in the current survey are compared
to data items from earlier surveys to ensure certain relationships are logical. The edit will determine the status of each
record to be either “dirty” or “clean” (i.e. failing or passing the edit requirements for consistency and reasonableness).
Records that fail edit requirements must be updated or certified by an analyst to be exempt from the failed edit
requirement. Only records that pass edit requirements are eligible for final summary.

Analysis Tools: Edited trout data are processed through an interactive analysis tool which displays data for all reports by
item. The tool provides scatter plots, tables, charts, and special tabulations that allow the analyst to compare an individual
record to similar records. Atypical responses and unusual data relationships become evident and Estimation Center staff
review them to determine if they are correct. The tool allows comparison to an agricultural operation’s previously
reported data to detect large changes in the operation. Data found to be in error are corrected, while accepted data are
retained.
Nonsampling Errors: Nonsampling errors are present in any survey process. These errors include reporting, recording,
and editing errors. Steps are taken to minimize these errors, such as comprehensive interviewer training, validation, and
verification of processing systems, application of detailed computer edits, and evaluation of the data via the analysis tools.
Estimators: The Trout Production Survey is a complete enumeration of all known trout operations in the selected states.
Trout operations are selected from the list of all agricultural operations, and new operations are added into the sample
when discovered. No coverage adjustment is made.
Response to the Trout Production Survey is voluntary. Some producers refuse to participate in the survey. Others cannot
be located during the data collection period and some submit incomplete reports. These nonrespondents must be
accounted for if accurate estimates of trout are to be made. For the Trout Production Survey, nonrespondents are
accounted for by adjusting the weights of the respondents. Since the entire population is sampled for the Trout Production
Survey, all operations have a sample weight of one. The adjustment occurs by stratum as the bounded strata represent
homogeneous groupings of similar sized farms. The largest stratum is unbounded and is made up of large and, often
unique, farms. Nonrespondents in this stratum must be manually imputed by Estimation Center statisticians and their
weights are not adjusted. The adjustment is performed by individual item on the questionnaire (total water area, inventory,
sales) so adjustments for item nonresponse (partial reports) and unit nonresponse (refusals and inaccessibles) are done in a
single calculation.
Two estimators are used to compute direct measures of the trout sales and distributed items. The “reweighted” estimator
and the “adjusted” estimator are computationally identical except in how the nonresponse adjustments are made. The
reweighted estimator uses a global weight adjustment across all usable reports. The nonresponse weight adjustment for the
adjusted estimator uses an additional piece of information. When a sampled farm refuses to cooperate, interviewers will
probe to determine whether an operation sold or distributed trout even though the number is not known. This
presence/absence indicator is used in the weight adjustment.
Point estimates, called direct expansions, for both estimators are calculated by multiplying the reported value by the
nonresponse-adjusted weight and summing to strata totals which are subsequently summed to obtain the state total.
Estimation: When all samples are accounted for, all responses fully edited and the analysis material is reviewed, each
state executes a summary to evaluate and analyze the data for which it is accountable. Since all states conduct identical
surveys, the samples can be pooled and national survey results computed. The summary results provide multiple point
estimates and information used to evaluate the quality of the survey estimates, such as response rates.
States are responsible for performing a detailed review of their survey results. Any irregularities revealed by the summary
must be investigated and, if necessary, resolved. Using the historical relationship of the survey estimates to the official
estimate, states must interpret the survey results and submit a recommended estimate to NASS headquarters in
Washington, DC for all data series in the program. The data are viewed in tabular and graphical form and a consensus
estimate established.
For the national estimates, NASS assembles a panel of statisticians to serve on the Agricultural Statistics Board (ASB).
The ASB reviews the national results and establishes the national estimates. The same estimators used in the state
summaries are produced by the national summary. The ASB follows the same approach the states do to determine state
estimates when determining the national estimates. In addition, the ASB examines results across all states and compares
the state level recommendations. Since larger sample sizes yield more precise results, NASS determines the national
estimates first and reconciles the state estimates to the national number. Survey based indicators can be impacted by
influential outliers, individual reports that have excessive influence on the estimates and are extremely unusual data for a
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Trout Production Methodology and Quality Measures (March 2014)
USDA, National Agricultural Statistics Service

given operation. NASS thoroughly reviews the survey data to identify these situations and consider their impact on the
survey results when establishing the official estimates.

Quality Metrics for Trout
Purpose and Definitions: Under the guidance of the Statistical Policy Office of the Office of Management and Budget
(OMB), the United States Department of Agriculture’s National Agricultural Statistics Service (NASS) provides data
users with quality metrics for its published data series. The metrics tables below describe the performance data for all
surveys contributing to the publication. The accuracy of data products may be evaluated through sampling and nonsampling error. The measurement of error due to sampling in the current period is irrelevant for a fully enumerated data
series. Non-sampling error is evaluated by response rates and the percent of the estimate from reported data.
Sample size is the number of observations selected from the population to represent a characteristic of the
population.
Response rate is the proportion of the sample that responds to the survey.
Percent of estimate from reported data is the value of a characteristic from respondent reports divided by the
value of a characteristic from respondent reports plus manually imputed reports expanded by the nonreponse
adjusted weights expressed as a percent.
Trout Production Survey Sample Size and Response Rates: To assist in evaluating the performance of the estimates in
the trout report, the sample size and response rates are displayed. Response rates overall for 2013 and 2014 are displayed.
Trout Survey Sample Size and Response Rates – United States: 2013-2014
2013

2014

Sample size

Response rate

Sample size

Response rate

(number)

(percent)

(number)

(percent)

Arkansas ......................................
California ......................................
Colorado .......................................
Georgia ........................................
Idaho ............................................
Michigan .......................................
Missouri ........................................
New York ......................................
North Carolina ..............................
Oregon .........................................

5
29
35
13
37
21
14
20
36
14

80.0
96.6
85.7
76.9
89.2
95.2
78.6
85.0
88.9
100.0

5
29
36
12
36
20
14
19
38
15

80.0
93.1
94.4
83.3
88.9
90.0
92.9
100.0
84.2
93.3

Pennsylvania ................................
Utah ..............................................
Virginia .........................................
Washington ..................................
West Virginia ................................
Wisconsin .....................................

55
20
24
23
25
43

100.0
90.0
83.3
100.0
56.0
95.3

52
22
23
23
24
42

90.4
100.0
87.0
78.3
91.7
97.6

Other States .................................

83

85.5

80

95.0

United States ................................

497

88.7

490

91.6

Trout Production Methodology and Quality Measures (March 2014)
USDA, National Agricultural Statistics Service

3

Trout Survey Percent of Estimate from Reported Data: To assist in evaluating the performance of the estimates in the
trout report, the percent of the estimate from reported data is displayed nationally by size category for sales and
distribution quantity and value.
Quality Measures for Trout Sales by Category – United States: 2012-2013
Percent of estimate from reported data
States

Number of fish sold

Value of sales

2012

2013

2012

2013

(percent)

(percent)

(percent)

(percent)

Fish 12" or Longer .........................
Fish 6" - 12" ..................................
Fish 1" - 6" ....................................

79.1
96.3
98.6

78.8
91.2
99.2

80.7
90.4
95.2

83.7
93.8
97.7

Quality Measures for Trout Distribution by Category – United States: 2012-2013
Percent of estimate from reported data
States

Number of fish distributed
2012
(percent)

Fish 12" or Longer .........................
Fish 6" - 12" ..................................
Fish 1" - 6" ....................................

Value of distributed fish

2013

2012

(percent)
91.8
99.2
95.8

2013

(percent)
99.5
98.0
98.4

(percent)
94.5
99.2
91.0

98.7
98.6
98.8

Information Contacts
Process
Estimation .............................................
Data Collection .....................................
Questionnaires and Editing ...................
Sampling ...............................................
Analysis and Estimators ........................
Dissemination and Webmaster ..............
Media Contact .......................................

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Unit
Livestock Branch
Survey Administration Branch
Editing and Questionnaire Branch
Survey Sampling Branch
Statistical Methods Branch
Data Dissimination Section
Public Affairs Section

Telephone
(202) 720-3570
(202) 720-3895
(202) 720-6201
(202) 720-3895
(202) 720-4008
(202) 720-7017
(202) 720-7017

Email
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]

Trout Production Methodology and Quality Measures (March 2014)
USDA, National Agricultural Statistics Service

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