Catfish Production Methodolgy and Quality Measures

Catfish Production Methodology and
Quality Measures
ISSN:

Released January 28, 2013, by the National Agricultural Statistics Service (NASS), Agricultural Statistics Board, United States Department
of Agriculture (USDA).

Annual Catfish Production Survey Methodology
Scope and Purpose: A Catfish Production Survey is conducted annually in January, which includes all states with known
catfish operations. Data are collected on water area, inventory, sales, and fish sold by point of first sale. In addition, the
number of catfish operations is captured. A second survey is conducted in July for three states. The July survey collects
data on water area and inventory.
Data collected on the number of operations, water area, inventory, sales, and fish sold by point of first sale are published
for seven states. States not required to collect data due to insufficient aggregate production will be estimated for by
Headquarters to be included in the Other States estimate. 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 catfish producing states.
Survey Timeline: The reference date for the January Catfish Production Survey is January 1 with a data collection period
of approximately three weeks. States complete data collection, analysis, summarization, and submission of estimates over
the three-week period ending in mid-January. 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 January on the date designated by the
Agricultural Statistics Board on its annual publications calendar.
Sampling: The target population for the Catfish Production Survey is all catfish farming operations that sell fish or have
the potential to sell fish in the selected states. A state is included for the Catfish Production Survey if it produces at least 1
percent of the total production for the United States. This survey is a complete census of the records on the National
Agricultural Statistics Service (NASS) List Frame with positively reported catfish production from a past survey. The List
Frame is a current and unduplicated list of agricultural operations, and all current catfish operations are assumed to be on
the list. If a new catfish operation is found at any time, the operation is added to the List Frame. Since this is a census of
catfish operations, all sample weights are 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 catfish operations.
Therefore, there is no area frame component to measure list incompleteness for the Catfish 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 catfish 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 Field Office
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 Catfish Production Survey is a complete enumeration of all known catfish operations in the selected
states. Catfish 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 Catfish 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 catfish are to be made. For the Catfish Production Survey, nonrespondents are
accounted for by adjusting the weights of the respondents. Since the Catfish Production Survey is a census, 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 catfish water area, inventory, and sales 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 the presence of water area and catfish inventory and sales even
though the number is not reported. 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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Catfish Production Methodology and Quality Measures (January 2013)
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 Catfish
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.
Catfish Production Survey Sample Size and Response Rates: To assist in evaluating the performance of the estimates
in the catfish report, the sample size and response rates are displayed. Response rates overall for 2012 and 2013 are
displayed.
Catfish Survey Sample Size and Response Rates – Selected States and United States: 2012-2013
2012

2013

Sample size

Response rate

Sample size

Response rate

(number)

(percent)

(number)

(percent)

Alabama ..........................................
Arkansas .........................................
California .........................................
Louisiana .........................................
Mississippi .......................................
North Carolina .................................
Texas ..............................................

139
86
37
14
233
32
83

77.7
89.5
73.0
85.7
88.0
87.5
72.3

125
56
29
8
211
23
58

75.2
92.9
79.3
87.5
88.2
73.9
72.4

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

90

83.3

62

72.6

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

714

82.9

572

81.5

Catfish Production Methodology and Quality Measures (January 2013)
USDA, National Agricultural Statistics Service

3

Catfish Production Percent of Estimate from Reported Data: To assist in evaluating the performance of the estimates
in the catfish report, the percent of the estimate from reported data for total water acres, the number of foodsize fish sold,
and the value of foodsize fish sales are displayed for the 7 published states, the other state category, and nationally.
Quality Metrics for Total Water Acres – Selected States and United States: 2012-2013
Percent of estimate from reported data
2012

2013

(percent)

(percent)

Alabama ..................................................................
Arkansas ..................................................................
California .................................................................
Louisiana .................................................................
Mississippi ...............................................................
North Carolina ..........................................................
Texas .......................................................................

84.1
90.2
79.6
100.0
81.5
96.4
77.4

83.2
83.6
78.1
95.2
82.0
94.2
79.1

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

86.0

85.6

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

83.4

82.7

Quality Metrics for Foodsize Fish Sold and Value of Sales – Selected States and
United States: 2011-2012
Percent of estimate from reported data
States

Number of fish sold

Value of sales

2011

2012

2011

2012

(percent)

(percent)

(percent)

(percent)

Alabama .........................................
Arkansas .........................................
California ........................................
Louisiana ........................................
Mississippi ......................................
North Carolina .................................
Texas ..............................................

81.9
94.0
90.7
100.0
83.9
97.1
67.6

80.6
89.6
79.6
94.6
86.7
94.5
84.6

83.7
93.0
88.0
100.0
79.9
97.2
77.0

78.2
85.3
80.0
83.8
79.6
94.7
79.1

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

85.8

89.3

84.2

88.5

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

83.6

85.0

82.5

79.7

Information Contacts
Process

Unit

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

Livestock Branch ...................................................
Program Administration Branch .............................
Editing and Questionnaire Branch .........................
Survey Sampling Branch .......................................
Statistical Methods Branch ....................................
Data Dissemination Section ...................................
Public Affairs Section .............................................

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Telephone
(202) 720-3570
(202) 690-8747
(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]

Catfish Production Methodology and Quality Measures (January 2013)
USDA, National Agricultural Statistics Service

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