Census Block Group Program for the 2010 Decennial Census-Final Criteria, 13829-13836 [E8-5075]

Agencies

• DEPARTMENT OF COMMERCE
• Bureau of the Census
• Census Bureau

[Federal Register Volume 73, Number 51 (Friday, March 14, 2008)]
[Notices]
[Pages 13829-13836]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E8-5075]


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DEPARTMENT OF COMMERCE

Bureau of the Census

[Docket Number 070126022-8027-02]


Census Block Group Program for the 2010 Decennial Census--Final 
Criteria

AGENCY: Bureau of the Census, Commerce.

ACTION: Notice of final criteria and program implementation.

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SUMMARY: Block groups are statistical geographic divisions of a census 
tract, defined for the tabulation and presentation of decennial census 
data. Block groups also will be used to tabulate and present period 
estimates from the American Community Survey (ACS) \1\ after 2010. 
Block groups provide the geographic framework within which the Bureau 
of the Census (Census Bureau) defines census blocks. Each block group 
comprises a reasonably compact and contiguous cluster of census blocks; 
up to nine block groups can be contained within a single census tract.
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    \1\ The ACS is conducted in the United States and in Puerto 
Rico. In Puerto Rico, the survey is called the Puerto Rico Community 
Survey. For ease of discussion, throughout this document the term 
ACS is used to represent both the survey that is conducted in the 
United States and in Puerto Rico.
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    This Notice announces the Census Bureau's final criteria for the 
Census Block Group Program for the 2010 Decennial Census. In addition, 
this Notice contains a summary of comments received to proposed 
criteria published in the April 6, 2007 Federal Register (72 FR 17337), 
as well as the Census Bureau's response to these comments. In response 
to comments received, the Census Bureau has modified its proposed 
criteria for the Census Block Group Program for the 2010 Decennial 
Census. Most provisions of the block group criteria for the 2010 Census 
remain unchanged from those used in conjunction with the 2000 Decennial 
Census, except as follows. First, the same population and housing unit 
thresholds, a minimum of 600 people or 240 housing units and a maximum 
of 3,000 people or 1,200 housing units, will apply to all types of 
populated block groups, including block groups delineated within 
American Indian reservations and off-reservation trust lands, the 
Island Areas, and encompassing group quarters, military installations, 
and institutions. Second, housing unit counts may be used instead of 
population counts in the delineation of block groups. Third, the 
delineation of special land use tracts will be permitted, and 
encouraged, for areas with special land uses (e.g., airports, military 
reservations, public forests, public parks, and special places/group 
quarters) with an official name. Finally, a geographic framework of 
tribal block groups, separate from the standard block groups defined 
within counties, will be defined within federally recognized American 
Indian reservations and/or off-reservation trust lands, subject to 
other population, housing, and boundary criteria contained in this 
document.
    Upon publication of the final criteria contained in this Notice, 
the Census Bureau will offer governments, organizations, and interested 
data users an opportunity to review and, if necessary, suggest updates 
to the boundaries and attributes of the block groups in their 
geographic area under the Participant Statistical Areas Program (PSAP). 
In addition to block groups, the PSAP also encompasses the review and 
update of census tracts, census designated places, and census county 
divisions (in selected states).

DATES: This notice's final criteria will be effective on March 14, 
2008.

FOR FURTHER INFORMATION CONTACT: The Geographic Standards and Criteria 
Branch, Geography Division, U.S. Census Bureau, via e-mail at 
geo.psap.list@census.gov or telephone at (301) 763-3056.

SUPPLEMENTARY INFORMATION:

I. History of Block Groups

    The Census Bureau first delineated block groups as statistical 
geographic divisions of census tracts for the 1970 Census, comprising 
contiguous combinations of census blocks for data presentation 
purposes. At that time, census block groups only existed in urbanized 
areas in which census blocks were defined. Block groups were defined 
without regard to political and

[[Page 13830]]

administrative boundaries, with an average population of 1,000, and to 
be approximately equal in area.
    As use of census block, block group, and census tract data 
increased among data users, the Census Bureau expanded these programs 
to cover additional geographic areas while redefining the population 
threshold criteria to more adequately suit data users' needs. The 1990 
Census was the first in which census blocks and block groups were 
defined throughout the entirety of the United States, Puerto Rico, and 
the Island Areas. For Census 2000, as with census tracts, the Census 
Bureau increased the number of geographic areas whose boundaries could 
be used as block group boundaries, and allowed tribal governments of 
federally recognized American Indian tribes with a reservation and/or 
off-reservation trust lands to delineate block groups without regard to 
state and/or county boundaries, provided the tribe had a 1990 Census 
population of at least 1,000.

II. Summary of Comments Received in Response to Proposed Criteria for 
the Census Block Group Program for the 2010 Census

    The April 6, 2007, Federal Register (72 FR 17337) requested comment 
on the proposed criteria for delineating block groups for the 2010 
Decennial Census which contained the following changes to the criteria 
used in the 2000 Decennial Census: (1) Increasing the minimum 
population and housing unit thresholds for block groups from 600 to 
1,200 persons; (2) using housing unit counts (as an alternative to 
population counts) in the delineation review and update of block 
groups; (3) applying the same population and housing unit thresholds to 
all types of populated block groups in the United States,\2\ including 
block groups delineated on American Indian reservations and/or off-
reservation trust lands,\3\ the Island Areas,\4\ and encompassing group 
quarters, military installations, and institutions; (4) allowing the 
delineation of block groups for large water bodies with areas of 
approximately 100 square miles or more, and special land uses (e.g., 
large airports or public parks) with an official name; and (5) allowing 
for geographic frameworks of tribal block groups (separate from the 
standard block groups defined within counties and standard census 
tracts) to be defined within federally recognized American Indian 
reservations and/or off-reservation trust lands.
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    \2\ For Census Bureau purposes, the United States includes the 
fifty states and the District of Columbia.
    \3\ The proposed criteria for the tribal statistical areas 
program will be outlined in a separate Federal Register notice. In 
the tribal statistical areas program, federally recognized American 
Indian tribes that have a reservation and/or off-reservation trust 
land may delineate census designated places and, if these areas have 
a population of 1,200 or greater, may delineate tribal tracts and 
tribal block groups for their reservation and off-reservation trust 
land.
    \4\ For Census Bureau purposes, the Island Areas includes 
American Samoa, the Commonwealth of the Northern Mariana Islands, 
Guam, the U.S. Virgin Islands, and the U.S. Minor Outlying Islands. 
The U.S. Minor Outlying Islands is an aggregation of nine U.S. 
territories: Baker Island, Howland Island, Jarvis Island, Johnston 
Atoll, Kingman Reef, Midway Islands, Navassa Island, Palmyra Atoll, 
and Wake Island.
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    The Census Bureau received letters (each containing comments on 
several issues) from 33 organizations and individuals on the proposed 
minimum population and housing unit thresholds in the review and update 
of block groups, the proposed use of housing unit counts in the review 
and update of block groups, and the permitted delineation of census 
tracts for large water bodies and special land use tracts for which a 
single coextensive block group would be delineated. Comments received 
are summarized below, as well as the Census Bureau's response to these 
comments.
    1. Minimum population and housing unit count thresholds in the 
review and update of block groups.
    The Census Bureau received 32 comments opposed to increasing the 
minimum population threshold for block groups from 600 to 1,200. Only 
one commenter favored the proposed increase citing the need to maintain 
statistical reliability. Nearly all commenters expressed strong concern 
about the resulting loss of geographic detail and the detrimental 
impact on demographic analysis for small geographic areas should the 
minimum population be increased to 1,200. Commenters opposed to an 
increased minimum threshold included metropolitan planning 
organizations, councils of governments, local governmental agencies, 
private sector data users, a state redistricting liaison, and members 
of the Census Advisory Committee Professional Associations.
    Additional research by the Census Bureau indicated that 
coefficients of variation for selected demographic characteristics did 
not improve substantially for block groups of 1,200 people compared to 
block groups of 600 people. Given the comments opposed to the proposed 
increased threshold, and taking into consideration the loss of 
geographic detail without substantive improvement to data quality and 
reliability, the Census Bureau will not change the minimum population 
threshold for block groups. The minimum block group threshold will 
remain at 600 people (240 housing units) for the 2010 Census. 
Participants reviewing and delineating block groups for the 2010 Census 
and data users utilizing the sample-based data for block groups must be 
aware of the sample data reliability issues for geographies with low 
populations and the appropriate uses for sample data for low population 
geographies. The Census Bureau will provide additional information 
about sample data reliability and appropriate uses of sample data for 
geographic areas with low populations in the PSAP guidelines.
    2. Using housing unit counts in the review and update of block 
groups.
    The Census Bureau received five comments in response to the 
proposed use of housing unit counts in the review and update of block 
groups as an alternative to population counts where appropriate. Four 
commenters supported the concept. Another supported the proposal, but 
requested more guidance on when housing units, instead of population, 
should be used to define block groups. Given the support of using 
housing unit counts in the review and update for census tracts, the 
Census Bureau will retain the concept in the final criteria for the 
2010 Census. Guidance as to when housing unit counts should be used in 
place of population counts in the review and update of census tracts 
will be discussed in this notice, and further detailed in the PSAP 
guidelines.
    3. Permitting the delineation of census tracts, with coextensive 
block groups, for large water bodies and special land uses.
    The Census Bureau received five comments in response to the 
proposed special land use tract and block group proposal. Four 
commenters representing various levels of local government, as well as 
nongovernmental organizations supported the concept. One commenter 
suggested that more discussion on the concept is needed to make an 
informed decision. Given the support of the special land use tract and 
coextensive block group designation, the Census Bureau will retain the 
concept in the final criteria for the 2010 Census.
    The Census Bureau received three comments in response to the 
proposed large water body tract and block group proposal. Two 
commenters supported the concept. One commenter opposed the concept, 
citing increased confusion and disorientation for data users with 
respect to what is commonly depicted on non-census maps. Based on this

[[Page 13831]]

comment and after additional internal review, the Census Bureau has 
determined not to retain the large water block group concept in the 
final criteria for the 2010 Census.

Changes to the Proposed Criteria as a Result of Public Comments

    Changes made to the final criteria (from the proposed criteria) in 
``Section III, General Principles and Criteria for Block Groups for the 
2010 Census'' are as follows:
    1. Section A, ``General Principles,'' subsection 3: renumbered in 
this notice as subsection 2. We moved this section to emphasize that 
block groups form the geographic framework within which the Census 
Bureau defines census blocks.
    2. Section A, ``General Principles,'' subsection 2: renumbered in 
this notice as subsection 3. The first sentence in this subsection has 
been reworded to provide greater specificity and clarity. We added the 
third sentence pertaining to the Census Bureau's disclosure rules; this 
sentence had appeared in Section B.1 of the previous notice. In the 
fourth sentence, we replaced ``local governments and planners'' with 
``PSAP participants'' because not all participants in the 2010 PSAP 
will be representatives of local governments or will be professional 
planners. We also added sentences that clarify the minimum population 
and housing unit thresholds, noting that any block group with a 
population or housing unit count less than the minimum threshold should 
be updated, and clarifying that the Census Bureau will use Census 2000 
population and housing unit counts to assess whether each block group 
submitted meets the minimum threshold criterion.
    3. Section A, ``General Principles:'' added subsection 4, which 
notes that housing unit counts may be used in the review and updating 
of block groups, particularly with regard to communities that may not 
have sufficient residential population present on the date of the 
decennial census, but will have larger populations at other times of 
the year and for which estimates may be reflected in the ACS.
    4. Section A, ``General Principles,'' subsection 4: renumbered in 
this notice as section 5. This subsection was moved because the new 
subsection 4 (see above) is closely related to issues discussed in 
subsection 3. We removed the reference to water body block groups since 
this proposed criterion has not been adopted in the final criteria.
    5. Section B, ``Changes to the Block Group Criteria for the 2010 
Census:'' this section was omitted from this notice as all changes are 
addressed in the final criteria.
    6. Section C, ``Block Group Criteria for the 2010 Census,'' 
subsection 1: Renumbered in this notice as subsection 3. We revised the 
order of the first few criteria for clarity. Section C in the April 6, 
2007 Federal Register (72 FR 17337) is now Section B in this Notice.
    7. Section C, ``Block Group Criteria for the 2010 Census,'' 
subsection 2: Renumbered in this notice as subsection 1, for clarity. 
We also changed the population threshold referenced in the subsection 
from 1,200 to 600, to reflect the decision to retain the latter as the 
minimum population threshold for a block group.
    8. Section C, ``Block Group Criteria for the 2010 Census,'' 
subsection 3: Renumbered in this notice as subsection 2, reflecting the 
decision to revise the order of the first few criteria listed. Removed 
the last sentence relating to water body block groups since this 
proposed criterion has not been adopted in the final criteria.
    9. Section C, ``Block Group Criteria for the 2010 Census,'' 
subsection 4: The second sentence was moved to the third sentence in 
this notice and the word ``permits'' was changed to ``requires'' to 
clarify that state and county boundaries must form block group 
boundaries.
    10. Section C, ``Block Group Criteria for the 2010 Census,'' 
subsection 5: Added the word ``measurement'' after ``area'' in both the 
text and the tables in this subsection. In addition, in subsection 5.c, 
all text relating to water body block groups was removed since this 
proposed criterion has not been adopted in the final criteria.
    11. Section D, ``Tribal Block Groups:'' We revised wording 
throughout the section to provide greater clarity. Discussion of tribal 
block groups is contained in Section C of this Notice.

III. General Principles and Criteria for Block Groups for the 2010 
Census

A. General Principles

    1. Block groups are statistical geographic divisions of a census 
tract, defined by the Census Bureau in cooperation with local officials 
and organizations, for the tabulation and dissemination of decennial 
census data, as well as period estimates of demographic and housing 
characteristics from the ACS.
    2. Block groups form the geographic framework within which the 
Census Bureau defines census blocks for use in tabulating and 
presenting decennial census data. Census blocks are numbered within 
block groups.
    3. The sample size for the ACS is smaller than the sample from the 
decennial census long form of previous censuses. As a general rule, 
estimates from programs providing sample data, including the ACS, for 
geographic areas with smaller populations will be subject to higher 
variances than comparable estimates for areas with larger populations 
(i.e., the sample data for smaller population geographies will likely 
be less reliable than the sample data for geographies with larger 
population). In addition, the Census Bureau's disclosure rules may have 
the effect of restricting the availability and amount of sample data 
published for geographic areas with small populations. Aiming to create 
block groups that fall between the minimum and maximum thresholds will 
improve the reliability and availability of data, and PSAP participants 
should consider these factors when defining their block groups.
    Therefore, each block group must encompass at least 600 people or 
at least 240 housing units unless it is coextensive with a flagged 
special land use tract, or is coextensive with a county with fewer than 
600 people. Any block group with a population or housing unit count 
less than the minimum threshold should be updated to meet or exceed the 
minimum threshold. The Census Bureau will use Census 2000 population 
and housing unit counts, with allowance made for growth since 2000, to 
assess whether each submitted block group meets this criterion. Program 
participants may submit local estimates as a surrogate for the Census 
2000 population and housing unit counts for a block group.
    4. With the advent of the ACS and the ``continuous measurement'' of 
characteristics of the population and housing based on a five-year 
average, there are some new issues to consider in the block group 
criteria. To accommodate this change, either population or housing 
units may be used in the review of block groups. The use of housing 
unit counts accommodates seasonal communities in which residents often 
are not present on the date of the decennial census, but will be 
present at other times of the year and for which estimates may be 
reflected in the ACS. The ACS is designed to produce local area data as 
of a 12-month period estimate (or an average); whereas, in the past 
local area data were only represented as of the April 1 census day.
    5. The Census Bureau recognizes that there are geographic areas 
that are not characterized by a residential population, and which local 
participants may wish to separate from populated block groups for 
analytical or

[[Page 13832]]

cartographic purposes or both. Such areas may be designated as special 
land use block groups to distinguish them from populated block groups. 
Special land use block groups must be designated as a specific type of 
land use (e.g., state park, municipal park) and have an official name, 
generally have little or no residential population or housing units, 
and must not create a noncontiguous block group. If located in a 
densely populated urban area, a special land use block group must have 
an area measurement of approximately one square mile or more. If 
delineated completely outside an urban area, a special land use block 
group must have an area of approximately 10 square miles or more. The 
Census Bureau recognizes that some special land use areas not intended 
for residential population, such as parks, may contain some population, 
such as caretakers or the homeless. Our intent is to allow for the 
delineation of parks and other special land use areas as separate block 
groups and therefore will accept such areas as block groups even if 
some residential population is present.

B. Block Group Criteria for the 2010 Census

    The criteria herein apply to the United States, including federally 
recognized American Indian reservations and off-reservation trust 
lands, Puerto Rico, and the Island Areas. The Census Bureau may modify 
and, if necessary, reject any proposals for block groups that do not 
meet these final criteria. In addition, the Census Bureau reserves the 
right to modify the boundaries and attributes of block groups as needed 
to meet the published criteria and/or maintain geographic relationships 
before the final tabulation geography is set for the 2010 Census.
    The Census Bureau sets forth the following criteria for use in 
delineating 2010 census block groups:
    1. Block groups must not cross census tract boundaries.
    This criterion takes precedence over all other criteria or 
requirements. By definition, because census tracts cannot cross county 
and state boundaries, neither can block groups. It is only permissible 
to define a block group with fewer than 600 people in a county that has 
a population less than 600, or as coextensive with a special land use 
tract.
    2. Block groups must cover the entire land and water area of each 
census tract.
    Because census tracts must cover the entire area of a county, by 
definition, block groups also must cover the entire area of each 
county.
    3. A block group must comprise a reasonable compact, contiguous 
land area.
    Noncontiguous boundaries are permitted only where a contiguous area 
or inaccessible area would not meet population or housing unit count 
requirements for a separate block group, in which case the 
noncontiguous or inaccessible area must be combined within an adjacent 
or proximate block group. For example, an island that does not meet the 
minimum population threshold for recognition as a separate block group 
should be combined with other proximate land to form a single block 
group. Each case will be reviewed and accepted at the Census Bureau's 
discretion.
    4. Block group boundaries should follow visible and identifiable 
features.
    To make the location of block group boundaries less ambiguous, 
wherever possible, block group boundaries should follow visible and 
identifiable features. The use of visible features makes it easier to 
locate and identify block group boundaries over time as the locations 
of many visible features in the landscape tend to change infrequently. 
The Census Bureau also requires the use of state and county boundaries 
in all states, and permits the use of incorporated place and minor 
civil division boundaries in states where those boundaries tend to 
remain unchanged over time (see Table 1).
    The following features are preferred as block group boundaries for 
the 2010 Census:
    a. State, county, and census tract boundaries must always be block 
group boundaries. This criterion takes precedence over all other 
boundary criteria or requirements.
    b. American Indian reservation and off-reservation trust land 
boundaries.
    c. Visible, perennial natural and cultural features, such as roads, 
shorelines, rivers, perennial streams and canals, railroad tracks, or 
above-ground high-tension power lines.
    d. Boundaries of legal and administrative entities in selected 
states.
    Table 1 identifies by state which minor civil division (MCD) and 
incorporated place boundaries may be used as block group boundaries.

                           Table 1.--Acceptable MCD and Incorporated Place Boundaries
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                                                                Boundaries of
                                                                   MCDs not
                                                               coincident with        All         Only conjoint
                                                  All MCD       the boundaries    incorporated     incorporated
                 Boundaries                      boundaries    of incorporated       place            place
                                                                 places that       boundaries       boundaries
                                                                themselves are
                                                                     MCDs
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Alabama.....................................  ...............  ...............  ...............               X
Alaska......................................  ...............  ...............  ...............               X
Arizona.....................................  ...............  ...............  ...............               X
Arkansas....................................  ...............  ...............  ...............               X
California..................................  ...............  ...............  ...............               X
Colorado....................................  ...............  ...............  ...............               X
Connecticut.................................               X   ...............               X   ...............
Delaware....................................  ...............  ...............  ...............               X
Florida.....................................  ...............  ...............  ...............               X
Georgia.....................................  ...............  ...............  ...............               X
Hawaii......................................  ...............  ...............  ...............               X
Idaho.......................................  ...............  ...............  ...............               X
Illinois....................................  ...............           X \a\   ...............               X
Indiana.....................................               X   ...............  ...............               X
Iowa........................................  ...............               X   ...............               X
Kansas......................................  ...............               X   ...............               X
Kentucky....................................  ...............  ...............  ...............               X
Louisiana...................................  ...............  ...............  ...............               X

[[Page 13833]]

 
Maine.......................................               X   ...............               X   ...............
Maryland....................................  ...............  ...............  ...............               X
Massachusetts...............................               X   ...............               X   ...............
Michigan....................................  ...............               X   ...............               X
Minnesota...................................  ...............               X   ...............               X
Mississippi.................................  ...............  ...............  ...............               X
Missouri....................................  ...............           X \b\   ...............               X
Montana.....................................  ...............  ...............  ...............               X
Nebraska....................................  ...............           X \a\   ...............               X
Nevada......................................  ...............  ...............  ...............               X
New Hampshire...............................               X   ...............               X   ...............
New Jersey..................................               X   ...............               X   ...............
New Mexico..................................  ...............  ...............  ...............               X
New York....................................               X   ...............               X   ...............
North Carolina..............................  ...............  ...............  ...............               X
North Dakota................................  ...............               X   ...............               X
Ohio........................................  ...............               X   ...............               X
Oklahoma....................................  ...............  ...............  ...............               X
Oregon......................................  ...............  ...............  ...............               X
Pennsylvania................................               X   ...............               X   ...............
Rhode Island................................               X   ...............               X   ...............
South Carolina..............................  ...............  ...............  ...............               X
South Dakota................................  ...............               X   ...............               X
Tennessee...................................  ...............  ...............  ...............               X
Texas.......................................  ...............  ...............  ...............               X
Utah........................................  ...............  ...............  ...............               X
Vermont.....................................               X   ...............               X   ...............
Virginia....................................  ...............  ...............  ...............               X
Washington..................................  ...............  ...............  ...............               X
West Virginia...............................  ...............  ...............  ...............               X
Wisconsin...................................  ...............               X   ...............               X
Wyoming.....................................  ...............  ...............  ...............               X
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\a\ Townships only.
\b\ Governmental townships only.

    e. Additionally, the following legally defined, administrative 
boundaries are permitted as block group boundaries:
    i. Barrio, barrio-pueblo, and subbarrio boundaries in Puerto Rico;
    ii. Census subdistrict boundaries in the U.S. Virgin Islands;
    iii. County and island boundaries (both MCD equivalents) in 
American Samoa;
    iv. Election district boundaries in Guam;
    v. Municipal district boundaries in the Commonwealth of the 
Northern Mariana Islands; and
    vi. Alaska Native regional corporation boundaries in Alaska, at the 
discretion of the Census Bureau, insofar as such boundaries are 
unambiguous for allocating living quarters as part of 2010 Census 
activities.
    f. When acceptable visible and governmental boundary features are 
not available for use as block group boundaries, the Census Bureau may, 
at its discretion, approve other nonstandard visible features, such as 
ridge lines, above-ground pipelines, intermittent streams, or fence 
lines. The Census Bureau may also accept, on a case-by-case basis, the 
boundaries of selected nonstandard and potentially nonvisible features, 
such as the boundaries of military installations, National Parks, 
National Monuments, National Forests, other types of parks or forests, 
airports, marine ports, cemeteries, golf courses, penitentiaries/
prisons, glaciers, or the straight-line extensions of visible features 
and other lines-of-sight.
5. Population, Housing Unit, and Area Measurement Thresholds
    The following are the population, housing unit, and area 
measurement threshold criteria for block groups (as summarized in Table 
2).

                                        Table 2.--Block Group Thresholds
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          Block group type                 Threshold type               Minimum                  Maximum
----------------------------------------------------------------------------------------------------------------
Standard & tribal block groups......  Population threshold...  600.....................  3,000.
                                      Housing Unit threshold.  240.....................  1,200.
Special land use block groups.......  Area measurement         1.0.....................  none.
                                       threshold within an
                                       urban area (square
                                       miles).

[[Page 13834]]

 
                                      Area measurement         10......................  none.
                                       threshold outside an
                                       urban area (square
                                       miles).
                                      Population thresholds..     (1) Little or none, or within standard block
                                                                                group thresholds.
----------------------------------------------------------------------------------------------------------------

    The same population and housing unit thresholds apply to all types 
of populated block groups, including block groups delineated within 
American Indian reservations and off-reservation trust lands, the 
Island Areas, and encompassing group quarters, military installations, 
and institutions. This should improve the availability and reliability 
of data for block groups that had a lower threshold for the 2000 
Decennial Census, and will create a single national standard.
    a. Census 2000 population counts should be used in census block 
group review in most cases. Housing unit counts should be used for 
block groups in seasonal communities that have no or low population on 
census day (April 1). Locally produced population and housing unit 
estimates can be used when reviewing and updating block groups, 
especially in areas that have experienced considerable growth since 
Census 2000.
    b. The housing unit thresholds are based on a national average of 
2.5 people per household. The Census Bureau recognizes that there are 
regional variations to this average, and will take this into 
consideration when reviewing all census block group proposals.
    c. For the 2010 Census, the Census Bureau will allow the 
delineation of special land use census tracts, and special land use 
block groups will be created coextensive with these special land use 
tracts. A special land use tract, and hence a special land use block 
group, must be designated as a specific land use type (e.g., state 
park), must have an official name (e.g., Jay Cooke State Park), have 
little or no residential population or meet population or housing unit 
thresholds, and must not create a noncontiguous tract/block group. In 
some instances, multiple areas can be combined to form a single special 
land use tract/block group if the land management characteristics are 
similar, such as a special land use tract/block group comprising 
adjacent federal and state parks. If the special land use tract/block 
group is delineated in a densely populated, urban area, the tract/block 
group must have an area of approximately one square mile or more. If 
the special land use tract/block group is delineated completely outside 
an urban area, the tract/block group must have an area of approximately 
10 square miles or more.
6. Identification of Block Groups
    a. A block group encompasses a cluster of census blocks. Each 
standard block group is identified using a single-digit number that 
will correspond to the first digit in the number of each block 
encompassed by the block group. For example, block group 3 includes all 
census blocks numbered in the 3000 range within a single census tract.
    b. The range of acceptable standard block group numbers is 1 
through 9. Block group numbers must always be unique within a census 
tract.
7. Block Group Types
    Table 3 below contains a summary of the types of block groups (with 
their respective population, housing unit and area measurement 
thresholds) that will be used for the 2010 Census.

                                     Table 3.--Summary of Block Group Types
----------------------------------------------------------------------------------------------------------------
                                   How distinct from
                                    standard block        Population         Housing unit      Area measurement
                                        groups            thresholds          thresholds          thresholds
----------------------------------------------------------------------------------------------------------------
Standard & tribal block groups..  Tribal block        Minimum: 600;       Minimum: 240;       none.
                                   groups are          Maximum: 3,000.     Maximum: 1,200.
                                   conceptually
                                   similar and
                                   equivalent to
                                   census block
                                   groups defined
                                   within the
                                   standard State-
                                   county-tract-
                                   block group
                                   geographic
                                   hierarchy used
                                   for tabulating
                                   and publishing
                                   statistical data.
Special land use block groups...  A block group       Little or none, or  Little or none, or  1.0 square mile
                                   coextensive with    within the          within the          within an urban
                                   a special land      standard block      standard block      area/10 square
                                   use tract,          group thresholds.   group thresholds.   miles outside an
                                   encompassing a                                              urban area.
                                   large airport,
                                   public park, or
                                   public forest
                                   with little or no
                                   population or
                                   housing units. In
                                   a densely
                                   populated, urban
                                   area, a special
                                   land use block
                                   group must be
                                   approximately 1.0
                                   square mile in
                                   area or greater.
                                   If delineated
                                   completely
                                   outside an urban
                                   area, a special
                                   land use block
                                   group must have
                                   an area of 10
                                   square miles or
                                   greater.
----------------------------------------------------------------------------------------------------------------

C. Tribal Block Groups

    Tribal block groups are statistical geographic entities defined by 
the Census Bureau in cooperation with tribal officials to provide 
meaningful, relevant, and reliable data for small geographic areas 
within the boundaries of federally recognized American Indian 
reservations and/or off-reservation trust lands. As such, they 
recognize the unique statistical data needs of federally recognized 
American Indian tribes. The delineation of tribal block groups allows 
for an unambiguous presentation of statistical data specific to a 
federally recognized reservation and/or off-reservation trust land 
without the imposition of state or county boundaries, which might 
artificially separate American Indian populations located within a 
single reservation and/or off-reservation trust land. To this end, the 
American Indian tribal participant \5\

[[Page 13835]]

may define tribal block groups that cross county or state boundaries, 
or both. Tribal block groups must be delineated to meet all other 
census block group criteria, and must be identified uniquely so as to 
clearly distinguish them from county-based block groups. The Census 
Bureau will address the type of identifiers required for tribal block 
groups in more detail in a separate Federal Register notice pertaining 
to American Indian statistical areas. Tribal block group boundaries 
will be held as census block boundaries. Census blocks, however, will 
be numbered uniquely within county-based block groups, and thus there 
will not be a direct relationship between a tribal block group 
identifier and census block numbers. Tribal block groups are 
conceptually similar and equivalent to census block groups defined 
within the standard state-county-tract-block group geographic hierarchy 
used for tabulating and publishing statistical data.
---------------------------------------------------------------------------

    \5\ For federally recognized American Indian tribes with 
reservations and/or off-reservation trust lands that have more than 
1,200 residents, the Census Bureau will offer the tribal government 
the opportunity to delineate tribal block groups and other tribal 
statistical geography on their reservation and/or off-reservation 
trust land. For federally recognized tribes with an American Indian 
reservation and/or off-reservation trust land that have fewer than 
1,200 residents, the Census Bureau will define one tribal tract and 
one tribal block group coextensive with the American Indian 
reservation and/or off-reservation trust land.
---------------------------------------------------------------------------

    In order to provide meaningful statistical geographic areas within 
the reservation and/or off-reservation trust land, as well as make 
meaningful and reliable data available for these areas and their 
populations, for the 2010 Census, tribal block group geography will be 
maintained separately from standard county-based block groups, and will 
be defined through a separate program designed specifically for tribal 
statistical geography. This differs from the procedure for Census 2000 
in which tribal block groups were defined for federally recognized 
American Indian reservations and/or off-reservation trust lands, and 
standard block groups were identified by superimposing county and state 
boundaries onto the Census 2000 tribal block groups.
    For Census 2000 products in which data were presented by state and 
county, the standard state-county-tract-block group hierarchy was 
maintained, even for territory contained within an American Indian 
reservation and/or off-reservation trust land. In such instances, the 
state/county portions of tribal block groups were identified as 
individual block groups, and these standard block groups may not have 
met the minimum population or housing unit thresholds, potentially 
limiting sample data reliability or availability for both the tribal 
block group and the derived standard block groups. The change for the 
2010 Census, creating standard block groups nationwide and maintaining 
tribal block groups as a completely separate set of geography from 
standard block groups in both geographic and data presentation 
purposes, eliminates, in part, these data issues from Census 2000.
    As with standard block groups submitted through the program, the 
tribal block groups would be submitted to the Census Bureau, and would 
be subject to review to ensure compliance with the final published 
criteria. Tribal block groups will be defined as part of a separate 
Tribal Statistical Areas Program (TSAP) for the 2010 Census. Detailed 
criteria pertaining to tribal block groups will be published in a 
separate Federal Register notice pertaining to all American Indian 
statistical areas defined through the TSAP.

IV. Definitions of Key Terms

    Alaska Native regional corporation (ANRC)--A corporate geographic 
area established under the Alaska Native Claims Settlement Act (Pub. L. 
92-203, 85 Stat. 688 (1971)), to conduct both, the business and 
nonprofit affairs of Alaska Natives. Twelve ANRCs cover the entire 
State of Alaska except for the Annette Island Reserve.
    American Indian off-reservation trust land (ORTL)--A federally 
recognized American Indian land area located outside the boundaries of 
an American Indian reservation whose boundaries are established by deed 
and over which a federally recognized American Indian tribal government 
has governmental authority.
    American Indian reservation (AIR)--A federally recognized American 
Indian land area with boundaries established by final treaty, statute, 
executive order, and/or court order and over which a federally 
recognized American Indian tribal government has governmental 
authority. Along with reservation, designations such as colonies, 
communities, pueblos, rancherias, and reserves apply to AIRs.
    Conjoint--A description of a boundary shared by two adjacent 
geographic entities.
    Contiguous--A description of areas sharing common boundaries, such 
that the areas, when combined, form a single piece of territory. 
Noncontiguous areas form disjoint pieces.
    Group quarters (GQ)--A place where people live or stay, in a group 
living arrangement, that is owned or managed by an entity or 
organization providing housing and/or services for the residents. This 
is not a typical household-type living arrangement. These services may 
include custodial or medical care, as well as other types of 
assistance, and residency is commonly restricted to those receiving 
these services. People living in GQs are usually not related to each 
other. GQs include such places as college residence halls, residential 
treatment centers, skilled nursing facilities, group homes, military 
barracks, correctional facilities, and workers' dormitories.
    Incorporated place--A type of governmental unit, incorporated under 
State law as a city, town (except in New England, New York, and 
Wisconsin), borough (except in Alaska and New York), or village, 
generally to provide governmental services for a concentration of 
people within legally prescribed boundaries.
    Minor civil division (MCD)--The primary governmental or 
administrative division of a county in 28 states and the Island Areas 
having legal boundaries, names, and descriptions. MCDs represent many 
different types of legal entities with a wide variety of 
characteristics, powers, and functions depending on the state and type 
of MCD. In some states, some or all of the incorporated places also 
constitute MCDs.
    Nonvisible feature--A map feature that is not visible on the 
ground, such as a city or county boundary through space, a property 
line, line-of-sight extension of a road.
    Special land use block group--Block group delineated coextensive 
with, or covering the same area as, the special land use tract.
    Special land use tract--Type of census tract that must be 
designated as a specific land use type (e.g., state park) and have an 
official name (e.g., Jay Cooke State Park), must have little or no 
residential population or housing units, and must not create a 
noncontiguous census tract. If delineated in a densely populated, urban 
area, a special land use tract must have an area of approximately one 
square mile or more. If delineated completely outside an urban area, a 
special land use tract must have an area of approximately ten square 
miles or more.
    TIGER--Topologically Integrated Geographic Encoding and Referencing 
database developed by the Census Bureau to support its mapping needs 
for the decennial census and other Census Bureau programs. The 
topological structure of the TIGER database defines the location and 
relationship of boundaries, streets, rivers, railroads, and other 
features to each other and to the numerous geographic areas for which 
the Census Bureau tabulates data from its censuses and surveys.
    Visible feature--A map feature that can be seen on the ground, such 
as a road, railroad track, major above-ground

[[Page 13836]]

transmission line or pipeline, river or stream, shoreline, fence, 
sharply defined mountain ridge, or cliff. A nonstandard visible feature 
is a feature that may not be clearly defined on the ground (such as a 
ridge), may be seasonal (such as an intermittent stream), or may be 
relatively impermanent (such as a fence). The Census Bureau generally 
requests verification that nonstandard features used as boundaries for 
the PSAP geographic areas pose no problem in their location during 
field work.

Executive Order 12866

    This notice has been determined to be not significant under 
Executive Order 12866.

Paperwork Reduction Act

    This program notice does not contain a collection of information 
subject to the requirements of the Paperwork Reduction Act, 44 U.S.C. 
Chapter 35.

    Dated: March 10, 2008.
Steve H. Murdock,
Director, Bureau of the Census.
 [FR Doc. E8-5075 Filed 3-13-08; 8:45 am]
BILLING CODE 3510-07-P