Volume 8; No. 4; Fall 1996
Understanding Census Tracts and Block Numbering Areas
The term "assessment area" may induce feelings of anxiety for
CRA officers knee-deep in census data and maps charting census tracts
and block numbering areas (BNAs). Although many banks have been able to
retain the boundaries of their old "service areas," many others
have had to redraw new assessment area boundaries in order to comply with
the new CRA regulations.
The guiding principle under the new CRA is that assessment areas must
"consist generally of one or more MSAs (metropolitan statistical
areas) or one or more contiguous political subdivisions, such as counties,
cities, or towns." Although the regulation states that banks may
adjust their boundaries to include "only the portion of a political
subdivision that it reasonably can be expected to serve," caution
is advised. The regulation goes on to say that an assessment area "must
consist only of whole geographies."
According to the regulation, the smallest possible "whole geography"
is a census tract or a BNA. A bank that draws its assessment area and
includes only parts of some census tracts or BNAs will have to redraw
its boundaries. In addition, a bank must be careful not to arbitrarily
exclude low- or- moderate income census tracts or BNAs from its assessment
Census tract numbers range from 0001 through 9499.99. BNAs range from
9501 through 9989.99, and both sets of numbers are unique within a county.
They usually have between 2,500 and 8,000 persons, though if the population
in either grows too large, they are divided; if the population shrinks,
the tracts or BNAs may be combined. You can purchase maps of census tracts
and BNAs from U.S. Government bookstores, from most universities, and
from the Superintendent of Documents in Pittsburgh, PA. A list of 12th
district data resource agencies is provided for your reference at the
end of this article.
What are the differences between census tracts and BNAs? Census tracts
are delineated for all metropolitan areas (as defined for the 1990 Census)
and other densely populated counties. They are established by local committees
and are considered relatively permanent. Tract boundaries may be revised,
however, by dividing or combining whole tracts or by making minor adjustments
in reaction to a local change, such as the removal of a road.
BNAs, on the other hand, are found in non-metropolitan counties and are
established by representatives at the state level or by the Census Bureau.
To date, very few BNAs have been converted to census tracts; this occurs
only when a county becomes part of a larger metropolitan area or when
local political pressure calls for conversion to a census tract.
Data collected for census tracts and BNAs include population, race, household
composition, education, employment, income, poverty, and housing information.
The Census Bureau updates this data on a frequent basis, but those updates
are generally done for the larger census divisions such as whole counties,
states, and the entire nation. Unfortunately, little information is routinely
collected at the level of census tract or BNA. An exception to that is
housing loan activity (in metropolitan areas only), which is mandated
by the Home Mortgage Disclosure Act (HMDA). HMDA data are collected annually
from individual banks, and aggregate reports are publicly available.
A variety of software products are now available for speedy mapping and
analysis of census data. Some companies will do the mapping for a fee,
although larger banks often invest in their own software. Census data
in these software programs are updated frequently, and though all of the
data can be mapped without computers, it generally takes much longer to
do it by hand.
The main thing to remember about assessment areas under the new CRA is
that they must be composed of contiguous political subdivisions, and that
portions of subdivisions can only be used if they are whole census tracts
or whole BNAs. Numbers and maps for tracts and BNAs located in the states
of the Twelfth Federal Reserve District can be obtained from the data
sources which follow.
Resource Centers for Census Data, Census Tract and BNA Maps
Many public libraries and university libraries are census depositories
and have information available in their government documents divisions.
Other possible resources are listed below.
Before requesting materials, we suggest that you have a clear idea of
the questions you want answered and the physical area you want covered.
These resource agencies charge fees for data extraction and/or maps, so
the better defined your needs are the less money you'll spend obtaining
the information. If you want "everything," be prepared to pay
for it and make sure you have the computer space and the knowledge to
use the data requested.
U.S. Department of Commerce
Bureau of the Census
Census Customer Services
Washington, D.C. 20233
|Superintendent of Documents
P.O. Box 371954
Pittsburgh, PA 15250-7954
Catalog available from the Office of Marketing:
Contact: Betty Jeffries
Department of Economic Security, Population Statistics
1789 W. Jefferson Street (1st floor, S.E. wing)
Phoenix, AZ 85007
Contact: Jan Nakamoto
Department of Business, Economic Development, and Tourism
250 S. Hotel Street, 4th floor
Honolulu, HI 96813
Contact: Javier Minjarez
Southern California Association of Governments
611 W. Sixth Street, 37th floor
Los Angeles, CA 90017
| Contact: Jeanine Smallwood
Association of Monterey Bay Area Governments
P.O. Box 809
Marina, CA 93933
| Contact: Dan Stone
Association of Bay Area Governments
P.O. Box 2050
Oakland, CA 94604-2050
| Contact: Data Center
Sacramento Area Council of Governments
3000 'S' Street, Suite 300
Sacramento, CA 95816-7056
| Contact: Linda Gage
California Department of Finance
Demographic Research Unit
915 'L' Street, Lower Level
Sacramento, CA 95814
916/322-4651 or 916/323-4086
| Contact: Eunice Tanjuaquio
San Diego Association of Governments
401 'B' Street, Suite 800
San Diego, CA 92101
Contact (for information only): Alan Porter
Idaho Department of Commerce
P.O. Box 83720
Boise, ID 83720-0093
(Maps available from Superintendent of Documents listed above)
Contact: Lin Nary
Nevada State Library and Archives
State Data Center
100 Stewart Street
Carson City, NV 89710
Contact: George C. Hough, Jr., Ph.D.
Center for Population Research & Census
Portland State University
P.O. Box 751
Portland, OR 97207-0751
Contact: State Data Center
Office of Financial Management
P.O. Box 43113
Olympia, WA 98504-3113
Portions of this article are excerpts from Community Dividend,
a publication produced by the Federal Reserve Bank of Minneapolis.