April 2001 Food Security Supplement Data File: Technical Documentation
Prepared by Mark Nord
Economic Research Service (ERS)
December 9, 2002
Revision history of this document
December 9, 2002—release of first draft
Overview
This document provides technical information on the Current Population
Survey Food Security Supplement (CPS-FSS) conducted by the U.S.
Census Bureau for the U.S. Department of Agriculture in April 2001.
The CPS-FSS is normally conducted once each year. In 2001 it was
conducted twice, in April and in December. The December data were
used as the basis of the annual USDA food security report for 2001.
The April Supplement was administered to only 6 of the 8 rotation
groups and was intended primarily to assess any seasonal effects
that might be present in the December collection period.
The CPS-FSS is available from the U.S. Census Bureau in three
formats: ASCII format on CD-ROM, ASCII format via the DataFerrett
system, and SAS transport format via the DataFerrett system.
The
Economic Research Service
Website provides additional documentation, a facsimile
of the questionnaire, and information on the concepts and
history of the food security measurement project.
Technical Description
The CD-ROM data file is in ASCII format and consists of 157,043
logical records. The length of each record is 1117 characters. Each
record represents one person in a surveyed household or one address
that was selected for the core labor force survey but that either
was vacant, was not a residence, could not be contacted, or refused
to participate. Noninterview households (16,775) are included in
the CD-ROM file with their noninterview status indicated. Interviewed
households (55,375) include 140,268 person records. Households in
rotation groups 1 and 5 (13,830) were not eligible for the Supplement.
Of the 41,545 eligible households, 34,330 households completed the
Food Security Supplement as well as the labor force survey and included
86,209 person records.
The DataFerrett
system files do not include noninterview households (but
do include interviewed households with Supplement data missing).
Data
files downloaded from DataFerrett, therefore, exclude noninterview
households and consist of 140,268 records comprising 55,375
households.
A subset of variables on each record contains data about the household
of which the person is a part. These variables have the same value
for all persons in the same interview household.
Contents of the Data File
The file includes data in three general categories:
(1) Monthly labor force survey data and recodes, collected by the
Census Bureau for the Bureau of Labor Statistics. These variables
are described briefly in the data dictionary. For concepts and definitions
underlying these data, users should refer to the technical documentation
for the CPS monthly labor force data available from the Bureau of
Labor Statistics. Included are geographic, demographic, income,
and employment data that may be of interest to those analyzing the
Food Security Supplement data.
(2) Food Security Supplement data, collected by the Census Bureau
for the United States Department of Agriculture. These data consist
of answers by household respondents to questions about household
food expenditures, use of food assistance programs, and experiences
and behaviors related to food security, food insecurity, and hunger.
All of the Food Security Supplement data are household-level data
except for the Supplement person weight.
(3) Food security and hunger scale and status indicators calculated
from the Food Security Supplement data by the Economic Research
Service of the U. S. Department of Agriculture. These indicate the
screening status of the household, as well as continuous and categorical
measures of food security status. They are all household-level variables.
Contents of the Food Security Supplement Questionnaire
A facsimile
of the Food Security Supplement questionnaire is available
on the ERS website and on the public-use data file CD-ROM
available from the Census Bureau. Variable names in the
data dictionary generally consist of the prefix HE (household
variable, edited) followed by the question number from
the questionnaire. The major sections are as follows:
(1) Food Spending (HES1A-HES8).
(2) Food Assistance Program Participation (HES9-HESP9).
(3) Food Sufficiency and Food Security (HESS1-HESSHM5). This section
includes the 18 food security and hunger questions that are used
to calculate the Household Food Security Scale.
(4) Ways of Avoiding or Ameliorating Food Deprivation - Coping
Strategies (HESC1-HESC4).
(5) Minimum Food Spending Needed (HES10-HES12)
Changes from Previous Years' Food Security Supplements
The following changes were introduced in the April 2001 Food Security
Supplement:
• Discontinued the split ballot test of variants of the
first three questions in the food security scale (HESS2A, HESS3A,
and HESS4A) conducted in 2000 for households in rotation 8.
• Continued the split ballot test of follow-ups to six
questions in the hunger and severe hunger series (HESHF2A, HESHF3A,
HESHF4A, HESSHF1A, HESSHF2A, HESSHF4A) initiated in 2000 for households
in rotation 8. The test question asks, "In months when [behavior
or experience occurred], how many days did this usually happen?"
The corresponding 30-day followup questions for these households
were skipped.
• Added to the data file three variables describing
the household's food security during the 30 days prior
to the survey (HRFS30M1, HRFS30M2, HRFS30M3). These
variables are based on the 30-Day Household Food Security
Scale described in A 30-Day Food Security Scale for
Current Population Survey Food Security Supplement Data
(E-FAN-02-015, Economic Research Service, USDA, August
2002). The scale is calculated from responses to questions
that were already included in the Supplement and did
not require any changes to the questionnaire.
Screening of the Food Security Supplement
The Food Security Supplement includes several screens to reduce
respondent burden and to avoid embarrassing respondents by asking
them questions that are inappropriate given other information they
have provided in the survey. The screener variables use information
from the monthly labor force core data as well as from the Food
Security Supplement. Households with incomes above 185 percent of
the poverty threshold (HRPOOR=2, estimated from HUFAMINC and HRNUMHOU)
that responded "no" to HES9 were not asked the questions
on participation in food assistance programs. Households with income
above 185 percent of poverty that registered no indication of food
stress on HES9 or HESS1 were not asked the rest of the questions
in the "Food Sufficiency and Food Security" section
or those in the "Ways of Avoiding or Ameliorating Food Deprivation"
section. There are also two "internal" screeners in
the main food security section (the questions that are used to calculate
the Household Food Security Scale). This series of questions is
divided into three blocks. After each of the first two blocks, households
that registered no indication of food stress in the preceding block
are skipped over the rest of the "Food Sufficiency and Food
Security" section.
The screening rules that determine whether a household was asked
the questions in the food security scale varied somewhat during
the first four years of fielding the Food Security Supplement. These
different screening procedures biased estimated prevalences of food
insecurity and hunger differently in each year. Adjustments must
be made for these differences to compare prevalences of food security
and hunger across years. This topic is discussed further below under
the heading "Food Security Scales and Screener Variables."
Screeners also were applied based on whether the household included
any children, so that households without children were not asked
questions that refer specifically to children. For this purpose,
persons 17 or younger are classified as children except those who
are household reference persons or spouses of household reference
persons (PERRP=1, 2, or 3).
Food Security Scales and Screener Variables
The main purpose of the Food Security Supplement is to provide information
about food security, food insecurity, and hunger in the nation's
households. Several variables are provided in the data file that
identify the food security status of each household during the 12
months or 30 days prior to the survey. All of these variables are
based on responses to a set or subset of 18 questions in the Supplement
that are indicators of food insecurity and hunger or to follow-up
questions that ask about occurrence of these conditions during the
30 days prior to the survey. The variables are as follows:
• Household Food Security Scale, 12-Month Reference Period
• HRFS12M1 is a categorical variable based on the scale
score (HRFS12M4) that classifies households in three categories:
food secure, food insecure without hunger, and food insecure with
hunger.
• HRFS12M2 is the same as HRFS12M1 except that
the food-insecure-with-hunger category is subdivided
to level 1 and level 2 hunger. The level 2 hunger category
corresponds operationally with the "Severe Hunger" category
described in Household Food Security in the United
States in 1995: Summary Report of the Food Security
Measurement Project and with the "Food Insecure
with Hunger (Severe)" category described in Guide
to Measuring Household Food Security – 2000,
both published by the Food and Nutrition Service.
• HRFS12M3 is the raw score—a count of the number
of questions in the 12-month Household Food Security Scale affirmed
by the household respondent
• HRFS12M4 is the scale score, a continuous score based
on fitting the data to a single parameter Rasch model using item
calibrations calculated from the 1998 data. Computed values range
from about 1 to 14. Scale scores for households that affirmed
no items cannot be calculated within the Rasch model. These households
are food secure, but the degree of their food security is not
known and may vary widely from household to household. They are
assigned scale scores of 6 to remind users that they require special
handling in analyses that assume linearity of the scale scores.
• Children's Food Security Scale, 12-Month Reference
Period. A second set of food security status variables
indicating the level of food stress among children in
the household is calculated from responses to the eight
questions in the scale that ask specifically about conditions
among the children.
• HRFS12M5 (two category children's hunger status
indicator).
• HRFS12M6 (raw score)
• HRFS12M7 (Rasch based scale score)
• Household Food Security Scale, 30-Day Reference Period.
The 30-Day Household Food Security Scale is similar to the corresponding
12-month scale except that it reflects conditions during the 30
days prior to the survey rather than those occurring at any time
during the year. However, the 30-day scale does not measure food
insecurity in the lower ranges of severity measured by the 12-month
scale. Thus, a substantial proportion of households that were
food insecure without hunger during the 30 days prior to the survey
are not identified as food insecure by the 30-day scale. The 30-day
food security variables are coded missing (-1) for households
in rotation 8. The 30-day follow-up questions were not administered
to those households because of a split-ballot test of experimental
follow-up questions. (See section below for information on appropriate
weights for these variables.)
• HRFS30M1 (three-category 30-day food security
status indicator)
• HRFS30M2 (raw score)
• HRFS30M3 (Rasch-based scale score)
• Household Food Security Scale, 12-Month Reference Period,
Adjusted for Comparability across All Years. The food security
variables described above are based on responses to the food security
indicator questions as they were administered in the April 2001
survey. They are directly comparable to the corresponding variables
in CPS-FSS conducted in August 1998 and later. A second set of
food security scale and status variables for the 12-Month Household
Food Security Scale are provided to facilitate comparisons to
years prior to 1998. These "common screen" variables
are adjusted for interyear differences in survey screening procedures
and are comparable to corresponding variables in all earlier years'
CPS-FSS data files. Prevalence estimates based on these common-screen
variables are comparable across all survey years.
• HRFS12C1 (three category food security status
indicator)
• HRFS12C2 (four category food security status
indicator)
• HRFS12C3 (raw score)
• HRFS12C4 (Rasch based scale score)
Common-screen adjusted variables are not provided for the children's
food security variables or for the 30-day household food security
variables. Adjustment of the Children's Food Security Scale
variables for screening differences is not necessary. The effects
of the different screening procedures on the measured prevalence
of hunger among children are negligible and the effects on the measured
prevalence of food insecurity at lower levels of severity among
children are small. Effects of screening differences across years
on 30-day prevalence rates have not been studied, but are expected
to be small or negligible at the hunger threshold and modest at
the lowest measured level of food insecurity. Users can adjust either
of these variables for screening differences using the screen variables
described below.
Two screener status variables are provided. HRFS12MS refers to
screening status under the screen that was applied when the survey
was administered (the "maximum-sample screen.") The
variable indicates whether the household was screened out at the
initial screen (before the first of the 18 scale questions), or
was screened out after the first or second blocks of questions,
or was not screened out and was asked all questions. Households
that were screened out at the initial screen without giving a valid
response to either screening question, or who were screened out
after the first or second block without having given a valid response
to any of the questions in the scale are coded as "Missing"
(-5) on HRFS12MS. The corresponding food security scale and status
variables for these households (HRFS12M1 through HRFS12M7 and HRFS30M1
through M3) are coded as "No Response" (-9).
HRFS12CS refers to screening status under the 1995-2001 common
screen. Categories are the same as for the maximum-sample screen
variable, and households that would have been screened out with no
valid responses to any of the indicator questions under the common
screen are coded as "Missing" (-5). Common-screen food
security scale and status variables (HRFS12C1 through HRFS12C4)
for these households are coded as "No Response" (-9).
Constructing Household Characteristics from Person Records
To compute some household characteristics such as household size,
presence of children, or presence of elderly members, it is necessary
to identify the records of all persons in the same household. Households
are uniquely and completely identified by State of residence (GESTCEN),
household identifier (HRHHID), and household serial suffix (HSERSUF).
Sort records within households by PERRP if the household reference
person record must be the first record in the household. To match
to other months' CPS files, add the HRMIS variable to the
household identification, adjusting one of the files for the difference
in survey month. For matching to the March Annual Demographic Supplement,
HRSERSUF may need to be recoded.
Weights—Estimating Population Distributions
of Person and Household Characteristics
The CPS is a complex probability sample, and interviewed households
as well as persons in those households are assigned weights so that
the full interviewed sample represents the total national noninstitutionalized
population. Initial weights are assigned based on probability of
selection into the sample, and weights are then adjusted iteratively
to match population controls for selected demographic characteristics
at State and national levels. There are two sets of household and
person weights in this data file: (1) labor force survey weights,
(2) Food Security Supplement weights.
The labor force survey weights, HWHHWGT for households and PWSSWGT
for persons, are positive for persons in all interviewed households
(except that person weights for persons in the armed forces are
zero or missing). These weights would be appropriate for analyzing
whether households or persons who completed the Supplement differed
from those who declined to complete the Supplement.
Households in rotations 1 and 5 were ineligible for the Supplement
in April 2001, and about 18 percent of eligible households completed
the core labor force survey but declined to complete the Food Security
Supplement. The Supplement weights, HHSUPWGT for households and
PWSUPWGT for persons, are adjusted for Supplement nonresponse so
that the Supplement respondents represent the national noninstitutionalized
population. These weights are appropriate for estimating household
distributions of variables in the Food Security Supplement, including
food security status.
Household weights are attached to all person records in the household.
To estimate household frequency distributions, the sample must be
limited to one record for each household. This is usually accomplished
by limiting the sample to records of household reference persons
(PERRP=1 or 2). Noninterview or nonsupplement households must be
excluded from these analyses based on HRINTSTA or HRSUPINT.
All weight variables have four implied decimal places in the CD-ROM
(the decimal point is not included). Divide the weight variables
by 10,000 for analysis in units or by 10,000,000 for analysis in
thousands of persons or thousands of households. The format of weight
variables downloaded from FERRET are somewhat unpredictable. Sometimes
they are in units; sometimes they have four implied decimal places.
These should be checked prior to use.
The 30-day food security questions were not administered to households
in rotation 8. Supplement weights may be used to calculate prevalence
rates, but supplement weights must be adjusted for loss of the 8th
rotation to calculate numbers of households or persons in a food
security category. The appropriate adjustment can be calculated
as the ratio of the weighted number of households (or persons) in
all 6 Supplement rotations to the weighted number of households
(or persons) in Supplement rotations except rotation 8.
Further Information
Information on the Federal Food Security Measurement Project, and
on survey and measurement issues, is available from:
United States Department of Agriculture, Economic Research Service
Contact Mark Nord 202-694-5433; marknord@ers.usda.gov
The Economic Research Service Food Security Briefing Room on the
Worldwide Web: http://www.ers.usda.gov/briefing/foodsecurity/
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