[Federal Register Volume 72, Number 66 (Friday, April 6, 2007)]
[Notices]
[Pages 17329-17337]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-6466]


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DEPARTMENT OF COMMERCE

Bureau of the Census

[Docket Number 070321065-7066-01]


Census Tract Program for the 2010 Census--Proposed Criteria

AGENCY: Bureau of the Census, Commerce.

ACTION: Notice of proposed program revisions and request for comments.

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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 of decennial census data and selected other 
statistical programs. Census tracts also will 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\ Includes parishes in Louisiana; boroughs, city and boroughs, 
census areas, and municipalities in Alaska; independent cities in 
Maryland, Missouri, Nevada, and Virginia; districts in American 
Samoa and 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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    Most provisions of the census tract criteria for the 2010 Census 
remain unchanged from those used in conjunction with Census 2000. 
However, based on consultation with data users and internal review the 
Bureau of the Census (Census Bureau) is proposing the following changes 
for the 2010 Census: (1) Lowering the minimum population threshold for 
census tracts; (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; (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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    In addition to proposed criteria, this notice includes a 
description of the changes from the criteria used for Census 2000 and a 
list of definitions of key terms used in the criteria.
    The Census Bureau is publishing this notice in the Federal Register 
to request comments from the public and other government agencies. The 
Census Bureau will respond to the comments received as part of the 
publication of final criteria in the Federal Register. After the final 
criteria are published in the Federal Register, the Census Bureau will 
offer designated governments or organizations an 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 under 
the Participant Statistical Areas Program (PSAP). In addition to census 
tracts, the program also encompasses the review and update of block 
groups, census designated places, and census county divisions.

DATES: Written comments must be submitted on or before July 5, 2007.

ADDRESSES: Please direct all written comments on this proposed program 
to the Director, U.S. Census Bureau, Room 8H001, mail stop 0100, 
Washington, DC 20233-0001.

FOR FURTHER INFORMATION CONTACT: Requests for additional information on 
this proposed program should be directed to Michael Ratcliffe, Chief, 
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

[[Page 17330]]

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. General Principles and Criteria for Census Tracts for the 2010 
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 
local governments and planners should consider these factors when 
defining their census tracts. Therefore, the Census Bureau proposes 
that any census tracts not flagged as a water body or special land use 
tract (General Principle 4) must encompass at least 1,200 people or at 
least 480 housing units. 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). 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 17331]]

[GRAPHIC] [TIFF OMITTED] TN06AP07.010

    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. The Census Bureau proposes the use of either population or 
housing units in the review of census tracts. 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. The Census Bureau proposes 
identifying these areas as water body tracts and special land use 
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 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/or 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. See, for example, Figure 2 below.

[[Page 17332]]

[GRAPHIC] [TIFF OMITTED] TN06AP07.011

B. Changes to the Census Tract Criteria for the 2010 Census

    Most provisions of the census tract criteria for the 2010 Census 
would remain unchanged from those used in conjunction with Census 2000 
with only the following exceptions:
    1. The minimum population threshold for census tracts would be 
1,200, lowered from the minimum threshold of 1,500 used in Census 2000. 
This change seeks to create a standard minimum threshold for census 
block groups and census tracts, in order to support the reliability and 
availability of sample data for these statistical geographies.
    2. Housing unit counts may be used instead of population counts in 
the review and update of tracts. This change seeks to accommodate 
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.
    3. For Census 2000, minimum population thresholds for census tracts 
varied. The minimum population threshold for census tracts delineated 
on American Indian reservations and off-reservation trust lands was 
1,000. This differed from the minimum threshold of 1,500 people for 
census tracts defined elsewhere in the United States, as well as in 
Puerto Rico and the Island Areas. Optimum populations for census tracts 
also varied: 4,000 in the United States and Puerto Rico, and 2,500 on 
American Indian reservations and in the Island Areas. The maximum 
population for a census tract in any of these areas was 8,000. In 
addition, for Census 2000, tracts that enclosed an institution, a 
military installation, or other ``special place'' had a minimum 
population requirement of 1,000 inhabitants, with no optimum or 
maximum.
    For the 2010 Census the same population and housing unit thresholds 
would apply to all types of populated tracts, including census tracts 
delineated on American Indian reservations and off-reservation trust 
lands, the Island Areas, and encompassing group quarters, military 
installations, and institutions. The Census Bureau proposes this change 
in order to aid in the availability and reliability of data for all 
tracts and to create a single national standard.
    4. The delineation of census tracts would be permitted, and 
encouraged, for the following types of geographic areas:
    a. Large water bodies with areas of approximately 100 square miles 
or more.
    b. Special land uses (for example, large airports, public parks, or 
public forests) with an official name.
    The Census Bureau would require that special land use tracts have 
little or no residential population. All such census tracts would meet 
all other tract criteria.
    5. A geographic framework of tribal tracts, separate from the 
standard census tracts defined within counties, may 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. This represents a change 
from the practice for Census 2000. The Census Bureau proposes this 
change to better recognize the unique statistical data needs of 
federally recognized American Indian tribes and their reservation and 
off-reservation trust lands.

C. Census Tract Criteria for the 2010 Census

    The criteria proposed 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 the established 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 proposes the following criteria for use in 
reviewing 2010 Census tracts:
    1. 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 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

[[Page 17333]]

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.
    2. A census tract must cover the entire land and water area of a 
county.
    In counties containing coastal waters, territorial sea, and 
portions of the Great Lakes, and very large, contiguous, inland water 
bodies, a single water body tract should be created for each discrete 
water body to provide for complete census tract coverage.
    3. 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 Census Bureau also permits the use of State 
and county boundaries in all States, and incorporated place and minor 
civil division boundaries in States where those boundaries tend to 
remain unchanged over time (see Table 1). 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.
    The following features are preferred as census tract boundaries for 
the 2010 Census:
    a. State and county boundaries must always be tract boundaries. 
This criterion takes precedence over all other criteria or requirements 
except for the population threshold criteria for tribal tracts on 
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 tract boundaries.

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

[[Page 17334]]

 
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 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 
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, or glaciers, or the straight-line extensions of visible 
features and other lines-of-sight.
    g. The boundaries of large water bodies and special land use 
tracts, including parks, forests, large airports, and military 
installations, provided the boundaries are clearly marked or easily 
recognized.
4. Population, Housing Unit, and Area Thresholds
    The Census Bureau proposes the following population, housing unit, 
and area threshold criteria for census tracts (as summarized in Table 
2).

                                           Table 2.--Tract Thresholds
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            Tract type                  Threshold type            Optimum             Minimum         Maximum
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Standard & tribal tracts..........  Population threshold.  4,000................           1,200           8,000
                                    Housing Unit           1,600................             480           3,200
                                     threshold.
Water body tracts.................  Area threshold         none.................             100            none
                                     (square miles).
Special land use tracts...........  Area threshold for an  none.................               1            none
                                     urban area (square
                                     miles).
                                    Area threshold         none.................              10            none
                                     outside an urban
                                     area (square miles).
----------------------------------------------------------------------------------------------------------------

    a. Population counts should be used in tract review in most cases. 
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 population 
growth has occurred since 2000 or is expected before 2010 for a census 
tract, the tract should not be merged if it has a Census 2000 
population of at least 1,100 or a housing unit count of at least 440 
and acceptable supporting evidence is supplied by the PSAP participant 
that population and/or housing unit growth has occurred since Census 
2000, or will likely occur before 2010, and has been sufficient to meet 
the minimum thresholds. 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.

[[Page 17335]]

    d. The Census Bureau may waive the maximum population and housing 
thresholds as required to achieve the objectives of this notice.
    e. For the 2010 Census, the Census Bureau encourages the 
delineation of special-use tracts in specific types of areas.
    i. 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.
    ii. A water body tract must encompass all or part of a territorial 
sea, coastal water, a Great Lake, or an inland water body at least 100 
square miles in area. If a water body meets this criterion and is in 
more than one county, each county can delineate a tract for its portion 
of the water body. Any islands within a qualifying water body should be 
included within a separate tract.
5. 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 9949 (but, see 5.c. below); tracts delineated 
specifically to complete coverage of large water bodies will be 
numbered from 9950 to 9989 in each county. All other tracts that fall 
within the 9950-9989 range must be renumbered. For Census 2000, water 
body tracts were all coded 0000. Each of these must be renumbered for 
the 2010 Census.
    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 are proposed to be a separate 
and distinct geographic entity.
    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.
6. Census Tract types
    Table 3 below contains a summary of the types of census tracts 
(with their respective population, housing unit and area 
characteristics) that the Census Bureau proposes to use for the 2010 
Census.

                                     Table 3.--Summary of Census Tract Types
----------------------------------------------------------------------------------------------------------------
                                   How distinct from
                                    standard census       Population         Housing unit       Area thresholds
                                        tracts            thresholds          thresholds
----------------------------------------------------------------------------------------------------------------
Standard & tribal tracts........  Tribal tracts are   Optimum: 4,000;...  Optimum: 1,600;     None.
                                   conceptually       Minimum: 1,200;...  Minimum: 480;.....
                                   similar and        Maximum: 8,000....  Maximum: 3,200....
                                   equivalent to
                                   census tracts
                                   defined within
                                   the standard
                                   State-county-
                                   tract-block group
                                   geographic
                                   hierarchy used
                                   for tabulating
                                   and publishing
                                   statistical data.
Water body tract................  A tract             Zero..............  Zero..............  100 square miles
                                   encompassing all                                            if an inland
                                   or part of a                                                water body.
                                   territorial sea,
                                   coastal water, a
                                   Great Lake, or an
                                   inland water body
                                   at least 100
                                   square miles in
                                   area.
Special land-use tract..........  A tract             Little or none....  Little or none....  1 square mile
                                   encompassing a                                              within an urban
                                   large airport,                                              area/10 square
                                   public park, or                                             miles outside an
                                   public forest                                               urban area.
                                   with little or no
                                   population or
                                   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.
----------------------------------------------------------------------------------------------------------------

D. 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 
reservation 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 reservations 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

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lands that have fewer than 2,400 residents, the Census Bureau will 
define one tribal tract and one tribal block group 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-block 
group geographic hierarchy used for tabulating and publishing 
statistical data.
    In order to provide meaningful statistical geographic areas within 
the reservation and/or off-reservation trust land as well as to make 
meaningful and reliable data available for these areas and their 
populations, the Census Bureau proposes that for the 2010 Census, 
standard census tracts be delineated nationwide, and the tribal tract 
geography be maintained separately and 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 or housing unit thresholds, therefore potentially 
limiting sample data reliability or availability for both the tribal 
tract and the derived standard tracts. The proposed 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 would be submitted to the Census Bureau, and would 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.

III. 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) 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.
    Coastal water--Water bodies between territorial seas and inland 
water, the encompassing headlands being more than one mile apart and 
less than 24 miles apart.
    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.
    Great Lakes' waters--Water area beyond one mile wide headland 
embayments located in any of the five Great Lakes: Erie, Huron, 
Michigan, Ontario, or Superior.
    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.
    Inland water--Water bodies entirely surrounded by land or at the 
point where their opening to coastal waters, territorial seas, or the 
Great Lakes is less than one mile across.
    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.
    Territorial seas--Water bodies not included under the rules for 
inland water, coastal water, or Great Lakes' waters, see above.
    TIGER[supreg]--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[supreg] database 
defines the location and relationship of boundaries, streets, rivers, 
railroads, and other features to each other and to the

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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.
    Water body tract--Type of tract encompassing territorial seas, 
coastal water, the Great Lakes, or inland water at least 100 square 
miles in area. If an inland water body meets this criterion, each 
county can delineate a tract for its portion of the water body.

Executive Order 12866

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

Paperwork Reduction Act

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

    Dated: April 3, 2007.
Charles Louis Kincannon,
Director, Bureau of the Census.
[FR Doc. E7-6466 Filed 4-5-07; 8:45 am]
BILLING CODE 3510-07-P