0660.0021.REVISED.SuppStmt.PartB.081009

SUPPORTING STATEMENT
NATIONAL TELECOMMUNICATIONS AND INFORMATION ADMINISTRATION
BROADBAND SUBSCRIPTION AND USAGE SURVEY
(SUPPLEMENT TO CENSUS BUREAU’SCURRENT POPULATION SURVEY)
OMB CONTROL NO. 0660-0021

B. COLLECTIONS OF INFORMATION EMPLOYING STATISTICAL METHODS
1. Describe (including a numerical estimate) the potential respondent universe and any
sampling or other respondent selection method to be used. Data on the number of entities
(e.g. establishments, State and local governmental units, households, or persons) in the
universe and the corresponding sample are to be provided in tabular form. The tabulation
must also include expected response rates for the collection as a whole. If the collection has
been conducted before, provide the actual response rate achieved.
The Current Population Survey (CPS) is a monthly survey conducted in approximately 60,000
occupied households throughout the United States, including approximately 10,000 households
from the monthly supplementary sample to improve state-level estimates of health insurance
coverage for low-income children, also known as the SCHIP expansion. This supplementary
sample has been part of the official CPS since July 2001. Twenty-six states plus the District of
Columbia contain this supplementary sample each month.
The CPS is a probability sample based on a stratified sampling scheme. In general, the CPS
sample is selected from lists of addresses obtained from the most recent decennial census and
updated for new construction.
a.

State-Based Design

In the first stage of sampling, primary sampling units (PSUs) are selected. These PSUs consist
of counties or groups of contiguous counties in the United States, and are grouped into strata.
The CPS is a state-based design. Therefore, all PSUs and strata are defined within state
boundaries and the sample is allocated among the states to produce state and national estimates
with the required reliability, while keeping total sample size to a minimum. The national
reliability requirement is a coefficient of variation (CV) of 1.9 percent or less on the monthly
estimate of unemployed, assuming an unemployment rate of 6 percent. The state reliability
requirement is a CV of 8 percent or less on the annual average estimate of unemployed,
assuming an unemployment rate of 6 percent. For New York and California, the state reliability
requirement applies to the following substate areas: New York City (the five boroughs only),
the balance of New York state, Los Angeles County, and the balance of California.
Each stratum consists of one or more PSUs. Within each stratum, a single PSU is chosen for the
sample, with probability proportional to its population as of the most recent decennial census (in
this case, Census 2000). This PSU represents the entire stratum from which it was selected.

In the case of strata consisting of only one PSU, the PSU is termed “self-representing.”
Sample PSUs from strata with more than one PSU are called “non self-representing.”
The sample PSUs are selected from each stratum using a statistical method which increases the
probability of keeping the same areas in the sample from one sample redesign to the next.
In total, 824 geographic areas from a total of 2,025 geographic areas in the United States are in
sample for the basic CPS.
A sample of addresses within the sample PSUs is obtained in a second step. Most of the sample
addresses are selected from census lists in a single stage of sampling within the selected PSU; for
a relatively small proportion, an additional stage of selection within the PSU is necessary.
b.

PSU Stratification

The variables chosen for grouping the non self-representing PSUs in each state into strata reflect
the primary interest of the CPS in maximizing the reliability of estimates of labor force
characteristics. Basically, the same set of stratification variables (from the Census 2000) were
used for each state: unemployment statistics by male, female; number of families with a female
head; and the proportion of occupied housing units with three or more people. In addition, the
number of persons employed in selected industries and the average monthly wage for selected
industries were used as stratification variables in some states. The industry-specific data arc
averages over the period 1990 through 1998 and were obtained from the Bureau of Labor
Statistics.
c.

Rotation System

Each sample is divided into eight approximately equal rotation groups. A rotation group is
interviewed for four consecutive months, temporarily leaves the sample for eight months and
then returns for four more consecutive months before retiring permanently from the CPS (after a
total of eight interviews). This rotation scheme has been in use since July 1953. The end result
of this rotation pattern is an improvement in the reliability of estimates of month-to-month
change as well as estimates of year-to-year change.

2. Describe the procedures for the collection, including: the statistical methodology for
stratification and sample selection; the estimation procedure; the degree of accuracy
needed for the purpose described in the justification; any unusual problems requiring
specialized sampling procedures; and any use of periodic (less frequent than annual) data
collection cycles to reduce burden.
Under the estimating methods used in the CPS, all of the results for a given month become
available simultaneously and are based on returns for the entire panel of respondents. The CPS
estimation procedure involves weighting the data from each sample person. The unbiased
weight, which is the inverse of the probability of the person being in the sample, is a rough

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measure of the number of actual persons that the sample person represents. Almost all sample
persons within the same state have the same unbiased weight. The unbiased weights are then
adjusted for noninterview, and a ratio adjustment procedure is applied.
a.

Noninterview Adjustment

The weights for all interviewed households are adjusted to account for occupied sample housing
units for which no information was obtained. Reasons for a noninterviewed household include
absence of the occupants, impassable roads, refusal of the occupant to participate in the survey,
or unavailability of the occupant for other reasons. The noninterview adjustment is performed
by noninterview cluster. Noninterview clusters are classified as either metropolitan or nonmetropolitan. PSUs classified as metropolitan are assigned to metropolitan clusters. PSUs
representing metropolitan areas of the same or similar size (based on Census 2000 population)
are grouped in the same noninterview cluster. Each metropolitan cluster is further divided into
two cells: central city and balance of the metropolitan area. Likewise, non-metropolitan PSUs
arc assigned to non-metropolitan clusters. All non-metropolitan areas in a state are placed
within the same noninterview cluster. Due to small sample sizes, a few non-metropolitan
noninterview clusters contain PSUs from more than one state.
b.

Adjusting Estimates to Population Controls

The distribution of the population selected in the sample may differ somewhat, by chance, from
that of the population as a whole in such characteristics as age, race, Hispanic origin, and sex.
Since these characteristics are correlated closely with labor force participation and other
principal measurements made from the sample, the latter estimates can be improved
substantially when weighted appropriately by the known distribution of these population
characteristics. This is accomplished through four adjustments as follows:
1)

First-stage ratio adjustment

In the CPS, some of the sample areas are chosen to represent both themselves and other
areas in the same state, but not in the sample; the remainder of the sample areas represent
only themselves. The first-stage ratio estimation procedure is designed to reduce that
portion of the variance resulting from requiring sample areas to represent areas not in
sample (i.e., non self-representing PSUs). Therefore, this adjustment procedure is
applied only to sample areas that represent other areas and is done by Black-alone /notBlack-alone cells at a state level. Each race cell is further divided into two age cells: age
0-15, and age 16 and older.
2)

National and state coverage adjustments

The national and state coverage adjustments were introduced in January 2003 in an effort
to improve the national and state estimates by race, Hispanic origin, sex, and age. The
national coverage adjustment is done by Black alone, White alone, Asian alone, and All
Other Race for non-Hispanics and by White alone, and All Other Race for Hispanics.
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The All-Other-Race category includes respondents who indicate they belong to more
than one race. These race/ethnicity categories are further divided into cells representing
various combinations of age and sex.
The national adjustment is performed by month-in-sample pair (1,5; 2,6; 3,7; and 4,8).
The cells used in the state coverage adjustment are defined by race category (Black
alone, not Black alone), age, and sex. The adjustment is performed either for each
month-in-sample pair or for all eight month-in-sample groups combined. The actual
cells used vary by state and race category.
3)

Second-stage ratio adjustment

The second-stage ratio adjustment modifies sample estimates in a number of age-sexrace-Hispanic origin groups to independently derived census-based estimates of the
civilian noninstitutional population (CNP) in each of these groups. This adjustment
reduces mean square error of sample estimates by reducing bias due to differential
coverage of the sampling frame. The adjustment is carried out in three steps and each set
of three steps is referred to as a “rake.” There are 10 cycles (or iterations) of raking.
Each step in each rake is done by month-in-sample pair.
In the first step, the sample estimates are adjusted for each state and the District of
Columbia to independent controls for the CNP by age and sex. There are three age cells
by sex (0-15, 16-44, 45 and over). The second step of the adjustment is done at the
national level by Hispanic origin status. Hispanic and non-Hispanic each have 13
age/sex cells, which are adjusted to nationwide independent controls. The third and final
step of the second-stage adjustment is performed by race (Black alone, White alone, All
Other Race). The All-Other- Race category includes respondents who indicate they
belong to more than one race. The cell division is by age/race/sex. Each of these cells is
adjusted to national independent population controls as in the previous step.
The entire second-stage adjustment procedure is iterated through 10 rakes. This iteration
ensures that the sample estimates of state and national population by the various age-sexrace-Hispanic origin categories will be virtually equal to the independent population
controls.

3. Describe the methods used to maximize response rates and to deal with nonresponse.
The accuracy and reliability of the information collected must be shown to be adequate for
the intended uses. For collections based on sampling, a special justification must be
provided if they will not yield "reliable" data that can be generalized to the universe
studied.
Basic CPS Reluctant Respondent Procedures: If a respondent is reluctant to participate in the
CPS, the interviewer immediately informs the regional office staff. The regional office sends a
follow-up letter to the household explaining CPS in greater detail and urging cooperation.
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The interviewer then recontacts the household and attempts the interview again. If this procedure
fails, a Supervisory Field Representative then contacts the household in an attempt to convert the
reluctant respondent. Methods used to interview reluctant households include conducting
telephone or personal interviews with the household, if so requested, and interviewing a
designated individual within the household. The CPS estimation procedure adjusts for household
nonresponse in its noninterview adjustment procedure. Individual item nonresponse is allocated
using a procedure in which the missing data are assigned from individuals whose data are
complete and have similar characteristics. The CPS household noninterview rate ranges between
7.5-9.5 percent monthly. Accuracy of the CPS data is maintained through interviewer training
and monthly home studies, monitoring of error and noninterview rates, and systematic
reinterviewing of CPS households. Each month about 7 percent of all CPS enumerators have
their assignments reinterviewed for quality control purposes. Errors uncovered during the
reinterview are discussed with the original interviewer and remedial action is taken. An
additional 7 percent of CPS enumerators have their assignments reinterviewed monthly to
measure response error.
Given that there are only five additional questions in this year's extra Internet questions series,
we do not anticipate any adverse impact on the supplement nonresponse rate. Should there be
any item nonresponse for the Internet questions, they will be allocated using a procedure in
which the missing data are assigned from individuals whose data are complete and have similar
characteristics.

4. Describe any tests of procedures or methods to be undertaken. Tests are encouraged as
effective means to refine collections, but if ten or more test respondents are involved OMB
must give prior approval.
The basic CPS program is not used as a vehicle for testing procedures or methods. There was,
however, an extensive program of testing conducted on CPS methods, procedures, and content.
This program, the Methods Development Survey (MDS), and its predecessor, the Methods Test
Panel (MTP), was conducted between May 1978 and December 1993.
The result of this testing is the new CPS Labor Force Instrument that is collected in a completely
automated CATI/CAPI environment. For further information on the testing procedures and
results see the February 1994 Employment and Earnings article titled, “Revisions to the Current
Population Survey Effective January 1994.”
5. Provide the name and telephone number of individuals consulted on the statistical
aspects of the design, and the name of the agency unit, contractor(s), grantee(s), or other
person(s) who will actually collect and/or analyze the information for the agency.
Individuals consulted on the statistical aspects of the CPS are Census/Demographic Statistical Methods Division
Ruth Ann Killion (301/763-3814)
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Patrick Flanagan (301/763-4290)
Carol Gunlicks (301/763-4241)

Census/Demographic Surveys Division
Cheryl L. Landman (301/763-3773)

Census/Responsible for data collection and processing
Kathy Creighton (301/763-3811)

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