[Federal Register Volume 73, Number 51 (Friday, March 14, 2008)]
[Notices]
[Pages 13836-13844]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-5076]


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DEPARTMENT OF COMMERCE

Bureau of the Census

[Docket Number 070321065-7903-02]


Census Tract 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: Census tracts are relatively permanent small-area geographic 
divisions of a county or statistically equivalent entity \1\ defined 
for the tabulation and presentation of data from the decennial census 
and selected other statistical programs. Census tracts will also be 
used to tabulate and publish estimates from the American Community 
Survey (ACS) \2\ after 2010. The primary goal of the census tract 
program is to provide a set of nationally consistent small, statistical 
geographic units, with stable boundaries, that facilitate analysis of 
data across time.
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    \1\ For the Census Bureau's purposes, the term ``county'' 
includes parishes in Louisiana; boroughs, city and boroughs, 
municipalities, and census areas in Alaska; independent cities in 
Maryland, Missouri, Nevada, and Virginia; districts and islands in 
American Samoa; districts in the U.S. Virgin Islands; municipalities 
in the Commonwealth of the Northern Mariana Islands; municipios in 
Puerto Rico; the areas constituting the District of Columbia and 
Guam. This notice will refer to all these entities collectively as 
``counties.''
    \2\ The ACS is conducted in the United States and in Puerto 
Rico. In Puerto Rico the survey is called the Puerto Rico Community 
Survey (PRCS). For ease of discussion, throughout this document the 
term ACS is used to represent the surveys conducted in the United 
States and in Puerto Rico.
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    This Notice announces the Bureau of the Census' (Census Bureau's) 
final criteria for the Census Tract 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 17329), as well as the Census Bureau's response to 
those comments. In response to comments received, the Census Bureau has 
modified its proposed criteria for the Census Tract Program for the 
2010 Decennial Census.
    Upon publication of the final census tract criteria contained in 
this Notice, the Census Bureau will offer governments, organizations, 
and interested data users the opportunity to review and, if necessary, 
suggest updates to the boundaries and attributes (e.g., tract code) of 
the census tracts in their geographic area as part of the Participant 
Statistical Areas Program (PSAP). In addition, to census tracts, the 
PSAP also encompasses the review and update of block groups, 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 
[email protected] or telephone at (301) 763-3056.

SUPPLEMENTARY INFORMATION:

I. History of Census Tracts

    In 1905, Dr. Walter Laidlaw originated the concept of permanent, 
small geographic areas as a framework for studying change from one 
decennial census to another in neighborhoods within New York City. For 
the 1910 Census, eight cities--New York, Baltimore, Boston, Chicago, 
Cleveland, Philadelphia, Pittsburgh, and St. Louis--delineated census 
tracts (then termed ``districts'') for the first time. No additional 
jurisdictions delineated census tracts until just prior to the 1930 
Census, when an additional ten cities chose to do so. The increased 
interest in census tracts for the 1930 Census is attributed to the 
promotional efforts of Howard Whipple Green, who was a statistician in 
Cleveland, Ohio, and later the chairman of the American Statistical 
Association's Committee on Census Enumeration Areas. For more than 
twenty-five years, Mr. Green strongly encouraged local citizens, via 
committees, to establish census tracts and other census statistical 
geographic areas. The committees created by local citizens were known 
as Census Tract Committees, later called Census Statistical Areas 
Committees.
    After 1930, the Census Bureau saw the need to standardize the 
delineation, review, and updating of census tracts and published the 
first set of census tract criteria in 1934. The goal of the criteria 
has remained unchanged; that is, to assure comparability and data 
reliability through the standardization of the population thresholds 
for census tracts, as well as requiring that their boundaries follow 
specific types of geographic features that do not change frequently. 
The Census Bureau began publishing census tract data as part of its 
standard tabulations beginning with the 1940 Census. Prior to that 
time, census tract data were published as special tabulations.
    For the 1940 Census, the Census Bureau began publishing census 
block data for all cities with 50,000 or more people. Census block 
numbers were assigned, where possible, by census tract, but for those 
cities that had not yet delineated census tracts, ``block areas'' 
(called ``block numbering areas'' [BNAs] in later censuses) were 
created to assign census block numbers.
    Starting with the 1960 Census, the Census Bureau assumed a greater 
role in promoting and coordinating the delineation, review, and update 
of census tracts. For the 1980 Census, criteria for BNAs were changed 
to make them more comparable in size and shape to census tracts. For 
the 1990 Census, all counties contained either census tracts or BNAs.
    Census 2000 was the first decade in which census tracts were 
defined in all counties. In addition, the Census Bureau increased the 
number of geographic areas whose boundaries could be used as census 
tract boundaries. It also allowed tribal governments of federally 
recognized American Indian tribes with a reservation and/or off-
reservation trust lands to delineate tracts 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 the Proposed Criteria 
for the Census Tract Program for the 2010 Decennial Census

    The April 6, 2007, Federal Register (72 FR 17329) requested comment 
on the proposed census tract criteria for the 2010 Decennial Census 
which contained the following changes to the criteria used in the 2000 
Decennial Census: (1)

[[Page 13837]]

Lowering the minimum population threshold for most census tracts from 
1,500 to 1,200; (2) using housing unit counts (as an alternative to 
population counts) in the review and update of tracts; (3) applying the 
same population and housing unit thresholds to all types of populated 
tracts within the United States,\3\ including census tracts delineated 
on American Indian reservations and off-reservation trust lands,\4\ 
Puerto Rico, the Island Areas,\5\ and encompassing group quarters, 
military installations, and institutions. For census tracts delineated 
in these areas, the 1,200 person threshold represents an increase from 
the Census 2000 threshold of 1,000 people. The minimum housing unit 
threshold for all census tracts would be 480. The maximum population 
threshold of 8,000 persons/3,200 housing units and the optimum of 4,000 
persons/1,600 housing units also will apply to all types of populated 
census tracts; (4) allowing the delineation of census tracts for large 
water bodies with areas of approximately 100 square miles or more and 
special land use (e.g., large airports or public parks) with an 
official name; and (5) allowing for geographic frameworks of tribal 
tracts (separate from the standard census tracts defined within 
counties) to be defined within federally recognized American Indian 
reservations and off-reservation trust lands.
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    \3\ For Census Bureau purposes, the United States includes the 
fifty States and the District of Columbia.
    \4\ 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 (CDPs), and, if these 
areas have a population of 2,400 or greater, may delineate tribal 
tracts and tribal block groups for their reservation and off-
reservation trust land.
    \5\ 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 comments from 11 individuals regarding 
the proposed use of housing unit counts in the review and update of 
census tracts, the permitted delineation of census tracts for large 
water bodies and special land uses, and the proposed tribal tract 
approach. Commenters represented a variety of agencies and 
organizations, including state and local government agencies, non-
profit policy research and analysis organizations, non-governmental 
organizations, professional societies, and private sector companies. 
Comments received by the Census Bureau are summarized below, as well as 
the Census Bureau's response to these comments.

1. Using Housing Unit Counts in the Review and Update of Tracts

    The Census Bureau received five comments in response to the 
proposed use of housing unit counts in the review and update of tracts 
and block groups as an alternative to population counts where 
appropriate. All five comments supported the concept, although one 
commenter requested more guidance on when housing units should be used 
to define tracts instead of population. 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.

2. Permitting the Delineation of Census Tracts for Large Water Bodies 
and Special Land Uses

    The Census Bureau received four comments in response to the 
proposal to encourage delineation of special land use tracts. Three 
commenters supported the concept. One commenter neither supported nor 
opposed the concept, but stated that more discussion about the concept 
is required. Given the support of the special land use tract 
designation, the Census Bureau will retain the concept in the final 
criteria for the 2010 Decennial Census.
    Three comments were received in response to the proposal to 
encourage delineation of large water body tracts. Two commenters 
supported the concept. One commenter opposed the concept, citing 
increased confusion and disorientation for data users with respect to 
what is commonly seen on non-census maps. Additional internal review 
and discussion of the large water body tract proposal led to a 
recommendation to not retain this requirement in the final criteria. 
Given the mixed response to the large water tract proposal, and 
subsequent internal review and discussion, the Census Bureau will not 
retain the large water tract concept in the final criteria for the 2010 
Decennial Census.

3. Allowing for a Geographic Framework of Tribal Census Tracts Defined 
Within Federally Recognized American Indian Reservations and Off-
Reservation Trust Lands, and Separate From the Standard Census Tracts 
Defined Within Counties

    The Census Bureau received two comments supporting the proposed 
tribal tract approach. In addition, two commenters requested 
clarification of the concept. The tribal tract approach will be fully 
explained in the ``American Indian Areas (AIAs) for the 2010 Census--
Proposed Criteria and Guidelines'' Federal Register notice to be 
published.
Changes to Proposed Criteria for the Census Tract Program for the 2010 
Decennial Census
    Changes made to the final criteria (from the proposed criteria) in 
``Section III, General Principles and Criteria for Census Tracts for 
the 2010 Census'' are as follows:
    1. Section A, ``General Principles,'' subsection 2, fourth 
sentence: 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. 
In the fifth sentence, we deleted the reference to water body tracts 
since this proposed criterion has not been adopted in the final 
criteria. We also changed the wording in the fifth sentence to improve 
the flow of the text and provide greater clarity.
    2. Section A, ``General Principles,'' subsection 2: added sentences 
referencing optimal population and housing unit thresholds for census 
tracts and the importance of the optimum threshold with regard to 
reliability and availability of sample-based data.
    3. Section A, ``General Principles,'' subsection 3: added text to 
help clarify why we are now permitting the use of housing unit counts 
in the review and updating of census tracts for the 2010 Census.
    4. Section A, ``General Principles,'' subsection 4: removed the 
reference to water body tracts since this proposed criterion has not 
been adopted in the final criteria.
    5. Section B, ``Changes to the Census Tract Criteria for the 2010 
Census:'' this section was omitted from this Notice as all changes are 
addressed in the final criteria.
    6. Section C, ``Census Tract Criteria for the 2010 Census:'' moved 
the following criterion ``Census tracts must not cross State and county 
boundaries,'' as the first listed criterion. Because this criterion 
supersedes all other criteria, we felt it required specific mention.

[[Page 13838]]

    7. Section C in the April 6, 2007 Federal Register (72 FR 17329) is 
now Section B.
    8. Section C, ``Census Tract Criteria for the 2010 Census:'' the 
criterion listed first, ``A census tract must comprise a reasonably 
compact and contiguous land area,'' is now listed third in this notice, 
partly as a result of the addition of the criterion relating to 
adherence to state and county boundaries, but also to produce a more 
logical flow to the criteria. As a result of this change, and the 
change listed above, all other criteria in this section have been 
renumbered.
    9. Section C, ``Census Tract Criteria for the 2010 Census,'' 
subsection 4.g: removed reference to water body tracts since that 
proposed criterion has been eliminated from the final criteria.
    10. Section C, ``Census Tract Criteria for the 2010 Census,'' 
subsection 5: added the word ``measurement'' after ``area'' in the 
title of the subsection, in the text, and in the table providing tract 
thresholds. In subsection 5a, we revised the wording to improve flow 
and provide greater clarity.
    11. Section C, ``Census Tract Criteria for the 2010 Census,'' 
subsection 5c: we revised the text in this subsection to provide 
greater clarity. We removed the reference to the level of population or 
housing units at which a tract need not be merged since this is not a 
specific criterion. The Census Bureau will provide a variety of 
examples in the PSAP guidelines to help guide participants when 
deciding whether to merge adjacent tracts.
    12. Section C, ``Census Tract Criteria for the 2010 Census,'' 
subsections 5d and 5e: we changed the order in which these subsections 
appear in the final criteria to provide a more logical flow to the 
presentation. In addition, we deleted the reference to water body 
tracts that appeared in subsection 5e of the proposed criteria.
    13. Section C, ``Census Tract Criteria for the 2010 Census,'' 
subsection 6b: removed criteria pertaining to codes for water body 
tracts since water body tracts have been deleted from the final 
criteria, and modified the high end of the range of allowable census 
tract identifiers from 9949 to 9989.
    14. Section C, ``Census Tract Criteria for the 2010 Census,'' 
subsection 7: added the word ``measurement'' after ``area'' in the text 
and table in this section.
    15. Section D, ``Tribal Tracts:'' in response to comments received, 
we revised wording throughout the section to provide greater clarity. 
Discussion of tribal tracts is contained in Section C of this Notice.

III. General Principles and Criteria for Census Tracts for the 2010 
Decennial Census

A. General Principles

    1. A century of census tract use has shown that continuity and 
comparability in tracts and their boundaries over time are of 
considerable importance to data users. Comparability has always been a 
goal in the census tract program since its inception for the 1910 
census; however, as the use of tract data increases, the importance of 
comparability increases as well. Maintaining comparability of tract 
boundaries over time facilitates longitudinal data analysis. The advent 
of the ACS and the averaging of sample data for tracts over a five-year 
span further underscore the need for consistent tract boundaries over 
time.
    Pursuant to this goal of continuity and comparability, the Census 
Bureau requests that where a census tract must be updated, for example 
to meet the minimum or maximum population or housing unit thresholds, 
that the outer boundaries of the tract not be changed, but rather that 
a tract be split into two or more tracts, or merged with an adjacent 
tract. The Census Bureau discourages changes to tract boundaries (that 
is, ``retracting''), except in specified circumstances, which the 
Census Bureau will review on a case-by-case basis.
    2. 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. 
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 census tracts 
that meet the optimal population of 4,000 and maintaining minimum 
thresholds will improve the reliability and availability of data, and 
PSAP participants should consider these factors when defining their 
census tracts. Therefore, each census tract must encompass at least 
1,200 people or at least 480 housing units unless it is flagged as a 
special land use tract, or is coextensive with a county with fewer than 
1,200 people. Any census tract with a population or housing unit count 
less than the minimum threshold should be merged with an adjacent 
census tract to form a single tract with at least 1,200 people or at 
least 480 housing units (Figure 1). Optimally, census tracts should 
have 4,000 people or 1,600 housing units. Meeting or exceeding the 
optimum thresholds will help improve the reliability of sample data for 
census tracts. The Census Bureau will use Census 2000 population and 
housing unit counts, with allowance made for growth since 2000, to 
assess whether each census tract submitted meets this criterion. 
Program participants may submit local estimates as a surrogate for the 
Census 2000 population and housing unit counts for a census tract.

[[Page 13839]]

[GRAPHIC] [TIFF OMITTED] TN14MR08.074

    3. 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 census tract 
criteria. To accommodate this change, either population or housing 
units may be used in the review of census tracts. 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 period 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 represented as of the April 1 census day.
    4. 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 tracts for analytical 
or cartographic purposes or both. Such areas may be designated as 
special land use tracts to distinguish them from populated census 
tracts. Special land use tracts 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 census tract. If located in 
a densely populated urban area, a special land use tract must have an 
area measurement of approximately 1 square mile or more. If delineated 
completely outside an urban area, a special land use tract 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 
tracts and therefore will accept such areas as tracts even if some 
residential population is present.
    5. To facilitate the analysis of data for American Indian tribes, 
and to recognize their unique governmental status, program participants 
are encouraged to merge, split, or redefine census tracts to avoid 
unnecessarily splitting American Indian reservations and off-
reservation trust lands. Each contiguous American Indian reservation 
and/or off-reservation trust land should be included, along with any 
necessary territory outside the reservation and/or off-reservation 
trust land, within a single census tract or as few census tracts as 
possible for the 2010 Census. This is the only situation in which 
retracting is encouraged. For example, see Figure 2 below.

[[Page 13840]]

[GRAPHIC] [TIFF OMITTED] TN14MR08.075

B. Census Tract Criteria for the 2010 Decennial 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 census tracts that do not 
meet these final criteria. In addition, the Census Bureau reserves the 
right to modify the boundaries and attributes of tracts 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 
Reviewing, Updating, and Delineating 2010 Census Tracts:
    1. Census tracts must not cross state or county boundaries.
    2. A census tract must cover the entire land and water area of a 
county.
    3. A census tract must comprise a reasonably compact and contiguous 
land area.
    Noncontiguous boundaries are permitted only where a noncontiguous 
area or inaccessible area would not meet population or housing unit 
count requirements for a separate census tract, in which case the 
noncontiguous or inaccessible area must be included within an adjacent 
or proximate tract. For example, an island that does not meet the 
minimum population threshold for recognition as a separate tract should 
be combined with other proximate land to form a single tract. Each case 
will be reviewed and accepted at the Census Bureau's discretion.
    4. Census tract boundaries should follow visible and identifiable 
features.
    To make the location of census tract boundaries less ambiguous, 
wherever possible, tract boundaries should follow visible and 
identifiable features. The use of visible features also makes it easier 
to locate and identify tract boundaries over time, as the locations of 
many visible features in the landscape tend to change infrequently. 
State and county boundaries must be census tract boundaries. The Census 
Bureau also 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 Census Tract Boundaries for 
the 2010 Census:
    a. State and county boundaries must always be census tract 
boundaries. This criterion takes precedence over all other criteria or 
requirements (except for tribal tracts on federally recognized American 
Indian reservations and/or off-reservation trust lands).
    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 census tract boundaries.

                           Table 1.--Acceptable MCD and Incorporated Place Boundaries
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                                                      Boundaries of MCDs
                                                        not coincident
                                                           with the
                                        All MCD          boundaries of     All incorporated      Only conjoint
                                      boundaries         incorporated      place boundaries      incorporated
                                                          places that                          places boundaries
                                                        themselves are
                                                             MCDs
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Alabama.........................  ..................  ..................  ..................                  X
Alaska..........................  ..................  ..................  ..................                  X
Arizona.........................  ..................  ..................  ..................                  X

[[Page 13841]]

 
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
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
----------------------------------------------------------------------------------------------------------------
\a\ Townships only.
\b\ Governmental townships only.

    e. Additionally, the following legally defined, administrative 
boundaries would be permitted as census tract 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 tract boundaries, the Census Bureau may, at 
its discretion, approve other nonstandard visible features, such as 
ridgelines, 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, or glaciers, or the straight-line

[[Page 13842]]

extensions of visible features and other lines-of-sight.
    g. The boundaries of parks, forests, large airports, and military 
installations, provided the boundaries are clearly marked or easily 
recognized.
    5. Population, Housing Unit, and Area Measurement thresholds.
    The following are the population, housing unit, and area 
measurement threshold criteria for census tracts (as summarized in 
Table 2).

                                           Table 2.--Tract Thresholds
----------------------------------------------------------------------------------------------------------------
              Tract type                    Threshold type           Optimum         Minimum          Maximum
----------------------------------------------------------------------------------------------------------------
Standard & tribal tracts.............  Population threshold....           4,000          1,200             8,000
                                      --------------------------------------------------------------------------
                                       Housing Unit threshold..           1,600            480             3,200
----------------------------------------------------------------------------------------------------------------
Special land use tracts..............  Area measurement                    none              1.0            none
                                        threshold for an urban
                                        area (square miles).
                                      --------------------------------------------------------------------------
                                       Area measurement                    none             10              none
                                        threshold outside an
                                        urban area (square
                                        miles).
                                      --------------------------------------------------------------------------
                                       Population threshold....    Little or none, or within the standard tract
                                                                                    thresholds
----------------------------------------------------------------------------------------------------------------

    a. Population counts should be used, in most cases, to review and 
update census tracts. Housing unit counts should be used for 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 tracts, 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 persons per household. The Census Bureau recognizes that there are 
regional variations to this average and will take this into 
consideration when reviewing all tract proposals.
    c. The Census Bureau recognizes the tension that exists between 
meeting the optimum population or housing unit threshold in a tract and 
maintaining tract comparability over time. For example, if sufficient 
population or housing unit growth has occurred since 2000 or is 
expected before 2010 for a census tract, based on Census 2000 data, was 
below the minimum thresholds, the tract should not be merged with 
another tract. Supporting evidence may be requested by the Census 
Bureau. However, should the census tract's population not increase as 
expected and does not meet either of the minimum thresholds in 2010, 
this may adversely affect the reliability and availability of any 
sample estimates for that tract. For this reason, the Census Bureau 
suggests merging the census tract with another if there is a 
possibility that anticipated growth will not be sufficient to meet 
minimum thresholds.
    d. For the 2010 Census, the Census Bureau allows the delineation of 
special land use tracts. A special land use tract 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, 
and must not create a noncontiguous tract. In some instances, multiple 
areas can be combined to form a single special land use tract if the 
land management characteristics are similar, such as a special land use 
tract comprising adjacent Federal and State parks. If the special land 
use tract is delineated in a densely populated, urban area, the tract 
must have an area of approximately one square mile or more. If the 
special land use tract is delineated completely outside an urban area, 
the tract must have an area of approximately 10 square miles or more.
    e. The Census Bureau may waive the maximum population and housing 
unit thresholds as required to achieve the objectives of this notice.
    6. Identification of Census Tracts.
    a. A census tract has a basic census tract identifier composed of 
no more than four digits and may have a two-digit decimal suffix.
    b. The range of acceptable basic census tract identifiers for the 
2010 Census is from 1 to 9989 (but, see 6.c. below); tracts delineated 
specifically to complete coverage of large water bodies will be 
numbered from 9950 to 9989 in each county.
    c. Census tracts delineated within or to primarily encompass 
American Indian reservations and/or off-reservation trust lands can 
continue to be numbered from 9400 to 9499. Local participants may opt 
to renumber these census tracts in a numeric range consistent with the 
rest of the county since tribal tracts will represent a separate and 
distinct geographic framework.
    d. Census tract identifiers must be unique within each county.
    e. Once used, census tract identifiers cannot be reused in a 
subsequent census to reference a completely different area within a 
county. If a tract is split, each portion may keep the same basic 4-
digit identifier, but each portion must be given a unique suffix. If a 
census tract that was suffixed for Census 2000 is split, each portion 
must be given a new suffix.
    f. The range of acceptable census tract suffixes is .01 to .98.
    7. Census Tract types.
    Table 3 provides a summary of the types of census tracts (with 
their respective population, housing unit, and area measurement 
thresholds) that the Census Bureau will use for the 2010 Census.

[[Page 13843]]



                                     Table 3.--Summary of Census Tract Types
----------------------------------------------------------------------------------------------------------------
                                    How distinct from        Population        Housing unit    Area  measurement
                                 standard census tracts      thresholds         thresholds         thresholds
----------------------------------------------------------------------------------------------------------------
Standard & tribal tracts.......  Tribal tracts are       Optimum: 4,000;    Optimum: 1,600;    none.
                                  conceptually similar    Minimum: 1,200;    Minimum: 480;
                                  and equivalent to       Maximum: 8,000.    Maximum: 3,200.
                                  census tracts defined
                                  within the standard
                                  state-county-tract-
                                  block group
                                  geographic hierarchy
                                  used for tabulating
                                  and publishing
                                  statistical data.
Special land use tract.........  A tract encompassing a  Little or none...  Little or none...  1.0 square mile
                                  large airport, public                                         within an urban
                                  park, or public                                               area/10 square
                                  forest with little or                                         miles outside an
                                  no population or                                              urban area.
                                  housing units. In a
                                  densely populated,
                                  urban area, a special
                                  land use tract should
                                  be approximately 1
                                  square mile in area
                                  or greater. If
                                  delineated completely
                                  outside an urban
                                  area, a special land
                                  use tract should have
                                  an area of 10 square
                                  miles or greater.
----------------------------------------------------------------------------------------------------------------

C. Tribal Tracts

    Tribal tracts 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 tracts allows for an 
unambiguous presentation of tract-level data specific to the American 
Indian reservation and/or off-reservation trust lands 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 may define tribal tracts that cross 
county or State boundaries, or both. For federally recognized American 
Indian tribes with reservations and/or off-reservation trust lands that 
have more than 2,400 residents, the Census Bureau will offer the tribal 
government the opportunity to delineate tribal tracts 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 lands that have fewer than 
2,400 residents, the Census Bureau will define one tribal tract 
coextensive with the reservation and/or off-reservation trust land. 
Tribal tracts must be delineated to meet all other census tract 
criteria, and must be numbered uniquely so as to clearly distinguish 
them from county-based census tracts. Tribal tracts are conceptually 
similar and equivalent to census tracts defined within the standard 
State-county-tract geographic hierarchy used for tabulating and 
publishing statistical data.
    Tribal tracts are defined to provide meaningful and reliable 
statistical data, particularly sample-based data, for small geographic 
areas within a reservation and/or off-reservation trust land. To 
accomplish this in as meaningful a manner as possible, tribal tract 
geography will constitute a geographic framework separate from standard 
county-based census tracts 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 tracts were 
defined for federally recognized American Indian reservations and/or 
off-reservation trust lands and standard census tracts were identified 
by superimposing county and state boundaries onto the tribal tracts.
    For Census 2000 products in which data were presented by state and 
county, the standard state-county-census tract 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 a tribal tract were identified as individual 
census tracts. These standard census tracts may not have met the 
minimum population thresholds; therefore, potentially limiting sample 
data reliability or availability for both the tribal tract and the 
derived standard tracts. The change in the tribal tract program for the 
2010 Census, creating standard, county-based census tracts nationwide 
and maintaining tribal tracts as a completely separate set of geography 
from standard tracts for both geographic information and data 
presentation purposes, seeks to eliminate, in part, these issues that 
existed with Census 2000 data.
    As with standard census tracts submitted through this program, the 
tribal tracts will be submitted to the Census Bureau, and will be 
subject to review to ensure compliance with the final published 
criteria. Tribal tracts will be defined as part of a separate Tribal 
Statistical Areas Program (TSAP) for the 2010 Census. Detailed criteria 
pertaining to tribal tracts 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--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

[[Page 13844]]

the areas, when combined, form a single piece of territory. 
Noncontiguous areas form disjoint pieces.
    Group quarters--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 group quarters are usually not related to each other. 
Group quarters 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. The 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, or 
line-of-sight extension of a road.
    Retracting--Substantially changing the boundaries of a tract so 
that comparability over time is not maintained.
    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 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 10 square miles or 
more.
    TIGER[reg]--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[reg] 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 transmission line or 
pipeline, river, 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. E8-5076 Filed 3-13-08; 8:45 am]
BILLING CODE 3510-07-P