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Block Groups for the 2020 Census-Proposed Criteria

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Bureau of the Census, Commerce.


Notice of proposed program and request for comments.


The Census Bureau is publishing this notice in the Federal Register to request comments from the public and other government agencies on block groups. 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 of the block groups in their geographic area under the Participant Statistical Areas Program (PSAP). In addition to block groups, the program also encompasses the review and update of census tracts, census designated places, and census county divisions.


Written comments must be submitted on or before May 16, 2018.


Please direct all written comments on this proposed program to Vincent Osier, Geographic Standards, Criteria, and Quality Branch, Geography Division, U.S. Census Bureau, Room 4H173, 4600 Silver Hill Road, Washington, DC 20233-7400. Email: Phone: 301-763-3056 (PSAP Hotline).

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Requests for additional information on this proposed program should be directed to Vincent Osier, Geographic Standards, Criteria, and Quality Branch, Geography Division, U.S. Census Bureau, Room 4H173, 4600 Silver Hill Road, Washington, DC 20233-7400. Email: Phone: 301-763-3056 (PSAP hotline).

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Block groups are statistical geographic subdivisions of a census tract defined for the tabulation and presentation of data from the decennial census and selected other statistical programs. Block groups will also be used to tabulate and publish estimates from the American Community Survey (ACS)[1] after 2020 and potentially data from other Bureau of the Census (Census Bureau) censuses and surveys.

There are no proposed changes to the existing block group criteria from the 2010 Census, only clarification. The history of block groups and changes implemented for the 2010 Census can be found in the Federal Register from March 14, 2008 (73 FR 13829).

I. General Principles and Criteria for Block Groups for the 2020 Census

A. General Principles

1. Block groups are statistical geographic subdivisions of a census tract and are the smallest geographic areas for which the Census Bureau provides sample data, primarily from the ACS 5-year period estimates.

2. Block groups form the geographic framework within which census blocks are numbered.

3. In order to ensure a minimal level of reliability in sample data and minimize potential disclosures of sensitive information, a block group should contain either at least 600 people or at least 240 housing units at minimum, and 3,000 people or 1,200 housing units at maximum. The housing unit criterion is used to accommodate areas that are occupied seasonally and may otherwise show a discrepancy between decennial and ACS figures.[2] For the ACS, block groups are not designed to be used individually, rather they provide a smaller geographic area than census tracts that allow data users to combine them to create larger geographic areas that may be more meaningful for their specific use.

4. The Census Bureau also recognizes that there are significant geographic areas that are characterized by unique populations (e.g., prisons or universities) or not characterized by residential populations at all (e.g., National Parks or large bodies of water), which local participants may wish to exclude from populated census tracts and/or block groups for either analytical or cartographic purposes. These areas may be designated as special use census tracts and/or block groups to distinguish them from standard populated census tracts and/or block groups. Special land and/or water use census tracts or block groups are not required, but if delineated they must be designated as a specific type of special use (discussed below); have an official name; ideally have no residential population or housing units or else meet all population or housing thresholds mentioned above; and, must not create noncontiguous block groups or census tracts. If located in an urban area, a special use block group must have an area measurement of approximately one square mile or more. If delineated completely outside an urban area, a special use block group must have an area of approximately 10 square miles or more. The Census Bureau recognizes that some special use areas not intended for residential population, such as parks, may contain some minimal population, such as caretakers or those experiencing homelessness. Since the primary purpose of block groups is to help provide high-quality statistical data about the population, the participant and the Census Bureau must decide if a special use tract would be useful in such a situation.

B. Criteria

The criteria herein apply to the United States, including federally recognized American Indian reservations (AIRs) and off-reservation trust lands (ORTLs), Puerto Rico, and the Island Areas[3] . The Census Bureau may modify and, if necessary, reject any proposals for block groups that do not meet the published criteria. In addition, the Census Bureau reserves the right to modify the boundaries and attributes of block groups as needed to meet the published criteria and/or maintain geographic relationships before or after the final tabulation geography is set for the 2020 Census.

The Census Bureau sets forth the following criteria for use in reviewing, updating, and delineating 2020 Census block groups:

1. Block groups must not cross census tract boundaries.

This criterion takes precedence over all other criteria or requirements. By definition, because census tracts cannot cross county [4] and state boundaries, Start Printed Page 6938neither can block groups. It is only permissible to define a block group with fewer than 600 people in a county that has a population less than 600, coextensive with a special use census tract, or as a special use block group delineated within a standard census tract.

2. Block groups must cover the entire land and water area of each census tract.

Because census tracts must cover the entire area of a county, by definition, block groups also must cover the entire area of each county.

3. A block group must comprise a reasonably compact and contiguous land area.

Noncontiguous boundaries are permitted only where a contiguous area or inaccessible area would not meet population or housing unit count requirements for a separate block group, in which case the noncontiguous or inaccessible area must be combined within an adjacent or proximate block group. For example, an island that does not meet the minimum population threshold for recognition as a separate block group should be combined with other proximate land to form a single block group. Each case will be reviewed and accepted at the Census Bureau's discretion.

4. Block group boundaries should follow visible and identifiable features.

To make the location of block group boundaries less ambiguous, wherever possible, block group boundaries should follow significant, visible, easily identifiable features. The use of visible features facilitates the location and identification of block group boundaries in the field, both on the ground and in imagery. The selection of permanent physical features also increases the stability of the boundaries over time, as the locations of many visible features in the landscape tend to change infrequently. If block group boundaries are changed, they should not be moved from a more significant feature (e.g., a highway or a major river) to a less significant feature (e.g., a neighborhood road or a small tributary stream). The Census Bureau also requires the use of state and county boundaries in all states to be used as census tract and block group boundaries. The Census Bureau also permits the use of incorporated place and minor civil division (MCD) boundaries in states where those boundaries tend to remain unchanged over time (see Table 1).

The following features are preferred as block group boundaries for the 2020 Census:

a. State, county, and census tract boundaries must always be block group boundaries. This criterion takes precedence over all other boundary criteria or requirements.

b. AIR and ORTL boundaries.

c. Visible, perennial, stable, relatively permanent natural and constructed 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 MCD and incorporated place boundaries may be used as block group boundaries.

e. Additionally, the following legally defined, administrative boundaries are permitted as block group boundaries:

i. Barrio, barrio-pueblo, and subbarrio boundaries in Puerto Rico;

ii. Census subdistrict and estate 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 2020 Census activities.

f. The boundaries of large parks, forests, airports, penitentiaries/prisons, and/or military installations, provided the boundaries are clearly marked or easily recognized in the field in imagery and on the ground.

g. When acceptable visible and governmental boundary features are not available for use as block group boundaries, the Census Bureau may, at its discretion, approve other nonstandard visible features, such as major ridgelines, above-ground pipelines, intermittent streams, or fence lines. The Census Bureau may also accept, on a case-by-case basis, relatively short stretches of boundaries of selected nonstandard and potentially nonvisible features, such as cadastral and parcel boundaries or the straight-line extensions or other lines-of-sight between acceptable visible features.

Table 1—Acceptable Minor Civil Division (MCD) and Incorporated Place Boundaries

StateAll MCD boundariesBoundaries of MCDs not coincident with the boundaries of incorporated places that themselves are MCDsAll incorporated place boundariesOnly conjoint incorporated place boundaries
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IowaX bX
KansasX aX
New HampshireXX
New JerseyXX
New MexicoX
New YorkXX
North CarolinaX
North DakotaXX
Rhode IslandXX
South CarolinaX
South DakotaX
West VirginiaX
a Townships only.
b Governmental townships only.

5. Population, Housing Unit, and Area Measurement Thresholds

The following are the population, housing unit, and area measurement threshold criteria for block groups (as summarized in Table 2). The same population and housing unit thresholds apply to all types of non-special use block groups, including those delineated for AIRs and ORTLs, the Island Areas, and encompassing group quarters, military installations, and institutions.

Table 2—Block Group Thresholds

Block group typeThreshold typesMinimumMaximum
Standard & tribal block groupsPopulation thresholds6003000.
Housing unit thresholds2401,200.
Special use block groupsArea measurement thresholds within an urban area1 square milenone.
Area measurement thresholds outside an urban area10 square milesnone.
Population thresholdsNone (or very little), or must be within the standard block group thresholds.

a. 2010 Census population counts should be used in census block group review in most cases. Housing unit counts should be used for block groups in seasonal communities that have little or no population on Census Day (April 1). Locally produced population and housing unit estimates can be used when reviewing and updating block groups, especially in areas that have experienced considerable growth since the 2010 Census.Start Printed Page 6940

b. The housing unit thresholds are based on a national average of 2.5 people per household. The Census Bureau recognizes that there are regional variations to this average, and will take this into consideration when reviewing all census block group proposals.

c. For the 2020 Census, the Census Bureau will allow the delineation of special use census tracts and special land use block groups will be created coextensive with these special use census tracts, but they are not required. A special use census tract, and hence a special use block group, must be designated as a specific use type (e.g., state park), must have an official name (e.g., Jay Cooke State Park), have no (or very little) residential population or meet population or housing unit thresholds, and must not create a noncontiguous census tract/block group. In some instances, multiple areas can be combined to form a single special land use census tract/block group if the land management characteristics are similar, such as a special land use census tract/block group comprising adjacent federal and state parks. If the special land use census tract/block group is delineated in a densely populated, urban area, the census tract/block group must have an area of approximately one square mile or more. If the special land use census tract/block group is delineated completely outside an urban area, the census tract/block group must have an area of approximately 10 square miles or more. Any resulting special use census tract/block group should be at least as large in area as the adjacent standard, populated census tracts/block groups.

6. Identification of Block Groups

a. A block group encompasses a cluster of census blocks. Each standard block group is identified using a single-digit number that will correspond to the first digit in the number of each census block encompassed by the block group. For example, block group 3 includes all census blocks numbered in the 3000 range within a single census tract.

b. The range of acceptable standard block group numbers is 1 through 9.

c. Block group numbers must be unique within a census tract.

7. Block Group Types

Table 3 provides a summary of the types of block groups (with their respective population, housing unit, and area measurement thresholds) that the Census Bureau will use for the 2020 Census.

Table 3—Summary of Block Group Types

Block group typesDistinction from standard block groupsPopulation thresholdsHousing unit thresholdsArea measurement thresholds
Standard block groupsMin: 600 Max: 3,000Min: 240 Max: 1,200None.
Tribal block groupsTribal block groups are conceptually similar and equivalent to census block groups defined within the standard state-county-tract-block group geographic hierarchy used for tabulating and publishing statistical dataMin: 600 Max: 3,000Min: 240 Max: 1,200None.
Special use block groupsA block group, usually coextensive with a special census tract, encompassing a large airport, public park, public forest, or large water body with no (or very little) population or housing unitsNone (or very little) or within the standard block group thresholdsNone (or very little) or within the standard block group thresholdsWithin an urban area: min. 1 square mile. Outside an urban area: min. 10 square miles.

C. Tribal Block Groups

Tribal block groups are statistical geographic entities defined by the Census Bureau in cooperation with tribal officials to provide meaningful, relevant, and reliable data for small geographic areas within the boundaries of federally recognized AIRs and/or ORTLs. As such, they recognize the unique statistical data needs of federally recognized American Indian tribes. The delineation of tribal block groups allows for an unambiguous presentation of statistical data specific to the federally recognized AIR and/or ORTL without the imposition of state or county boundaries, which might artificially separate American Indian populations located within a single AIR and/or ORTL. To this end, the American Indian tribal participant may define tribal block groups that cross county or state boundaries, or both. For federally recognized American Indian tribes with AIRs and/or ORTLs that have fewer than 1,200 residents, the Census Bureau will define one tribal census tract and one tribal block group coextensive with the AIR and/or ORTL. Tribal block groups must be delineated to meet all other census block group criteria, and must be identified uniquely so as to clearly distinguish them from county-based block groups. The Census Bureau will address the type of identifiers required for tribal block groups in more detail in a separate Federal Register notice pertaining to all American Indian areas, including statistical areas defined through PSAP. Tribal block group boundaries will be held as census block boundaries. Census blocks, however, will be numbered uniquely within county-based block groups and thus there will not be a direct relationship between a tribal block group identifier and the census block numbers. Tribal block groups are conceptually similar and equivalent to census block groups defined within the standard state-county-tract-block group geographic hierarchy used for tabulating and publishing statistical data.

In order to provide meaningful statistical geographic areas within the AIR and/or ORTL, as well as make meaningful and reliable data available for these areas and their populations, tribal block group geography is maintained separately from standard, county-based block groups. This change was first introduced for the 2010 Census, creating standard block groups nationwide and maintaining tribal block groups as a completely separate set of geography from standard block groups for both geographic and data presentation purposes, and eliminates, in part, the reliability and availability data issues for the tribal block groups Start Printed Page 6941and the derived standard block groups that were present in Census 2000.[5]

As with standard block groups submitted through this program, the tribal block groups are submitted to the Census Bureau, and are subject to review to ensure compliance with the published criteria. Detailed criteria pertaining to tribal block groups will be published in a separate Federal Register notice pertaining to all American Indian areas, including statistical areas defined through PSAP.

I. Definitions of Key Terms

Alaska Native Regional Corporation (ANRC)—A corporate geographic area established under the Alaska Native Claims Settlement Act (Pub. L. 92-203, 85 Stat. 688 (1971)) to conduct both the business and nonprofit affairs of Alaska Natives. Twelve ANRCs cover the entire State of Alaska except for the Annette Island Reserve.

American Indian off-reservation trust land (ORTL)—An area of land located outside the boundaries of an AIR, whose boundaries are established by deed, and which are held in trust by the U.S. federal government for a federally recognized American Indian tribe or members of that tribe.

American Indian reservation (AIR)—An area of land 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.

Census county division (CCD)—Areas delineated by the Census Bureau in cooperation with state, tribal, and local officials for statistical purposes. CCDs have no legal function and are not governmental units. CCD boundaries usually follow visible features and usually coincide with census tract boundaries. The name of each CCD is based on a place, county, or well-known local name that identifies its location.

Conjoint—A description of a boundary line shared by two adjacent geographic entities.

Contiguous—A description of areas sharing common boundary lines, more than a single point, such that the areas, when combined, form a single piece of territory. Noncontiguous areas form disjoint pieces.

Group quarters—A location 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 and in imagery 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 census tract so that comparability over time is not maintained.

Special use census tract/block group—Type of census tract or block group that must be designated as a specific use type (e.g., state park or large lake) and have an official name (e.g., Jay Cooke State Park or Lake Minnetonka), should have no (or very little) population or housing units, and must not create a noncontiguous census tract/block group. If delineated in a densely populated, urban area, a special use census tract/block group must have an area of at least one square mile. If delineated completely outside an urban area, a special use census tract/block group must have an area of at least 10 square miles.

Statistical geographic entity—A geographic entity that is specially defined and delineated, such as block group, CDP, or census tract, so that the Census Bureau may tabulate data for it. Designation as a statistical entity neither conveys nor confers legal ownership, entitlement, or jurisdictional authority.

Visible feature—A map feature that can be seen on the ground and in imagery, 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.

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Dated: January 31, 2018.

Ron S. Jarmin,

Associate Director for Economic Programs, Performing the Non-Exclusive Functions and Duties of the Director, Bureau of the Census.

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1.  The ACS is conducted in the United States and in Puerto Rico. In Puerto Rico, the survey is called the Puerto Rico Community Survey. For ease of discussion, throughout this document the term ACS is used to represent the surveys conducted in the United States and in Puerto Rico.

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2.  “Occupied seasonally” refers to seasonal communities in which residents often are not present on the date of the decennial census, but will be present at other times of the year and for which estimates may be reflected in the ACS. The ACS is designed to produce local area data as of a 12-month period estimate (or an average).

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3.  For Census Bureau purposes, the United States typically refers to only the fifty states and the District of Columbia, and does not include the U.S. territories (Puerto Rico, the Island Areas, and the U.S. Minor Outlying Islands). The Island Areas include American Samoa, the Commonwealth of the Northern Mariana Islands, Guam, and the U.S. Virgin Islands. The U.S. Minor Outlying Islands are 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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4.  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; and, the areas constituting the District of Columbia and Guam. T his notice will refer to all these entities collectively as “counties.”

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5.  For Census 2000, tribal block groups were defined for federally recognized AIRs and/or ORTLs, and standard block groups were identified by superimposing county and state boundaries onto the Census 2000 tribal block groups. For Census 2000 products in which data were presented by state and county, the standard state-county-tract-block group hierarchy was maintained, even for territory contained within an AIR and/or ORTL. In such instances, the state-county portions of tribal block groups were identified as individual block groups, and these standard block groups may not have met the minimum population or housing unit thresholds, potentially limiting sample data reliability or availability for both the tribal block groups and the derived standard block groups.

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[FR Doc. 2018-02624 Filed 2-14-18; 8:45 am]