TIME: Almanac 1990/1990 Time Magazine Compact Almanac, The (1991)(Time).iso/time/cal/pop1

Text File | 1991-05-13 | 17KB | 306 lines

                                                                              ««Two Hundred Years and Counting:

Census Geography  



   The success of the census depends not only on how well the Census
Bureau locates all living quarters and collects complete information
for each occupant but also on how accurately this information is
linked to its specific geographic location.

   All geographic areas used by the census fall into one of two cate-
gories; they are either "statistical areas" or "political and admin-
istrative areas," which typically have their boundaries set by law or
statutes. Examples of political areas are states, cities, congressional
districts, American Indian reservations, and voting districts.

   The Census Bureau defines statistical areas to meet the needs of the
census and users of statistics. Ideally, each such area is a single,
contiguous piece of territory. Examples of statistical areas are MSAs
(metropolitan statistical areas established by the OMB), census
tracts, block groups, and census blocks. Census blocks are the smallest
geographic statistical unit used for enumerating housing units and
reporting census data.

   Most census geography conforms to a hierarchy in which large areas
are formed by combining smaller areas. Statistics from small units of
geography can, therefore, be combined to provide information for more
than 25 different types of larger geographic areas.(4)

   For the 1990 Census, a key geographic statistical unit is the census
tract. The  Census Bureau and committees of local government officials
have created some 49,000 census tracts. There are also over 11,000
"block numbering areas," or BNAs, which are similar to census tracts
but are located almost exclusively in nonmetropolitan areas. BNAs are
defined by state offices or by the Census Bureau, with advice from
state officials.

   Within each census tract or BNA are up to nine subdivisions called
"block groups," which are used as a framework for numbering census
blocks. In cities and other urban areas, census blocks tend to be the
same as city blocks. In suburban and more sparsely-settled areas, the
census blocks-which are defined primarily by roads and by other visible
features of the landscape-may be large in area and irregular in shape.

   A major difference between the 1990 and earlier censuses is that,
for the first time, the entire United States, as well as Puerto Rico
and the outlying areas, has been divided into about 7.5 million census
blocks, 3 times the number in 1980. This improvement will allow the
Census Bureau to report its findings for all areas at a greater level
of detail than before.


Computer Geography

   Without modern computers, there could be no modern census. This fact
is as true of the census geographic support program as it is of field
operations or data tabulation. For the 1980 Census, the geographic
procedures were barely adequate to the task, largely because they were
not computerized.

   "For the 1980 Census, we prepared the three major geographic tools-
maps, address reference files, and geographic reference files-in inde-
pendent operations involving a great deal of clerical work," reports
Peter A. Bounpane, Assistant Director for Decennial Census. Because
they were constructed independently, each of these three products
described the same portion of the earth in a slightly different way.
"These processes were slow and error-prone, leading to production
delays, mistakes, and inconsistencies."

   Beginning in 1981, as results from the 1980 Census were still being
tabulated, the Bureau began to create a new computerized geographic
system-"TIGER," for "Topologically Integrated Geographic Encoding and
Referencing." TIGER is a completely new system that uses modern
computer technology to avoid the kinds of errors that plagued the 1980
Census geographic program.(5)

   Working with the U.S. Geological Survey, and primarily using the
Survey's 1:100,000-scale national map series, the Bureau has success-
fully built a geographic computerized data base. While building such
a data base is a complex procedure, it basically converts into machine-
readable format or "digitizes," individual geographic features from a
printed map. Each type of geographic feature is assigned a unique
computer code in the data base that differentiates it from all other
features.

   With its new geographic data base the Census Bureau can readily pro-
duce by computer a variety of consistent maps--maps for enumerators to
use while listing residential addresses or following up at housing units
that did not return census questionnaires; maps for district offices to
use in determining enumerator assignments; and maps to supplement the
data that will be published from the 1990 Census. The Census Bureau
will prepare individual maps for over 300,000 separate enumerator
assignment areas and over 39,000 governmental units, displaying the
names and boundaries of most data collection and tabulation areas.(6)

   Because all census geography now exists in a single computer file,
many address lists and statistics collected in the census can be linked
directly to the file. It is far less time consuming to update the
file. All changes are automatically reflected in all products created
from the file. "The TIGER System integrates into one computer file all
the geographic information that we produced separately for the 1980
Census," Peter Bounpane notes. This is an impressive accomplishment.

   As well as improving census operations, the TIGER System will make
possible a variety of other computerized geographic products. "It is
easy to let one's imagination conjure up new and exciting products--
full-color maps of data distributions, microcomputer-based geographic
information systems, all the maps for the entire country on a laser
disk, direct access to census data tabulations through a 'map' dis-
played on a color graphics computer terminal," writes Robert W. Marx,
Chief of the Census Bureau's Geography Division.(7)


Data Products

   If the census were simply a headcount used to achieve representative
government, its job would be over once the people were counted and the
totals provided to the President and state governors. But the census
is also extensively used by virtually every public and private organi-
zation. Demand for census data has grown with each census in recent
years. After spending billions of dollars to take the census, many
people believe the government has an obligation to provide billions of
dollars of benefits from its statistics.

   To understand census data products, it is useful to consider a basic
concept: The larger the geographic area, the more detailed subject mat-
ter information is available; the smaller the area, the less detail.
The Census Bureau cannot publish all of the data it gathers because
would all drown in the resulting sea of statistics. For the approxi-
mately 7.5 million census blocks, it will produce only headcounts and
a few basic characteristics from the short-form questionnaire. For the
nation as a whole, the 50 states, metropolitan areas, and other large
geographic units, it will produce detailed population and housing
statistics. This concept also helps determine which statistics the
Census Bureau releases on computer tape or in printed reports. A pop-
ulation profile of the United States is most useful as a printed
national summary publication, while detailed population characteristics
at the census-tract level for all 50 states will be most conveniently
used on computer tapes.

   Following the 1980 Census, the Bureau was not able to complete all
of the publications it had planned because of unexpected budget and
processing limitations. The Bureau's planners have tried to learn from
this experience to improve the publication program for 1990 and, in
particular, promise more timely release of data products. Once the
computer tapes containing redistricting statistics have been completed,
the first general purpose computer tape will become available during
the middle of 1991, and the first printed report will follow 6 to 8
weeks later. There will be a steady flow of data products until the
last product is released, scheduled for the latter part of 1993.(8)

   These products will be similar to those from the 1980 Census, but
with a few important changes. Following the 1980 Census, one of the
computer tapes most in demand was paid for not by the government it-
self but by a consortium of private organizations. This file presented
detailed demographic data by ZIP Code; the Census Bureau will produce
its own ZIP Code computer tape with 1990 data. But Summary Tape
File 5, which contains detailed cross-tabulations from the long-form
questionnaire, is being discontinued because of limited interest from
data users for this product after 1980.(9)

   Printed publications have been the principal means of releasing
census data since 1790, when the complete census report filled just 56
pages. Costs of printing have risen sharply in recent years, however,
and the data to be published have proliferated. The number of pages
published by the Bureau rose from about 100,000 in 1960, to 200,000
in 1970, and 300,000 in 1980. Estimates for 1990 are around 500,000
pages. Printed reports remain the most widely used data product from
the Census Bureau. At the same time, the computing capabilities of
census data users has risen dramatically in the past decade, making
computer files of greater potential value.(10)

   The Census Bureau will also provide data on compact disks (CD-ROM)
because this medium has much greater data storage capacity and flexi-
bility, and prices for this technology are decreasing. The Bureau is
also exploring the possibility of making data available on floppy
disks for use with microcomputers.

   In addition to computer tapes and printed reports, the Census
Bureau also releases data on microfiche. Microfiche was used as a
product medium for the first time in the 1980 Census. Microfiche is
cumbersome to use for large amounts of data, but it provides compact
storage and is inexpensive. When budget cuts following the 1980 Census
forced the Census Bureau to cancel plans for printed reports of data
for the nation's 2.5 million blocks, the Bureau provided this infor-
mation on microfiche instead.


Computer Tape Files

   The Summary Tape Files are the basic vehicles for releasing census
data. Printed reports and microfiche in turn are created from these
files. There will be two Summary Tape Files that provide data from
the short-form census questionnaire received by everyone and two that
provide more detailed data from the long-form (sample) questionnaire.
The tapes are released on a state-by-state basis as soon as tabula-
tions for the individual states have been completed.

   Summary Tape Files receive their name from the fact that they are
summaries of data, aggregated from the millions of responses to the
census questionnaires. Summary Tape File 1 (STF1) will include popu-
lation and housing counts and a few characteristics from the short-
form questionnaire, similar in content to the 1980 STF1. There will
be four files within STF1 (A, B, C, and D), providing different geo-
graphic presentations of the data.

   Summary Tape File 2 (STF2), which will comprise three files, will
also provide data tabulations from the short-form questionnaire, in-
cluding more extensive data for race and ethnicity (Questions 4 and 7
on the questionnaire).

   Summary Tape File 3 (STF3) and Summary Tape File 4 (STF4) will con-
tain data from the long-form questionnaire, similar to the comparable
tapes released after the 1980 Census. There will be four files with
STF3, including data for states and specified areas below the state
level, 5-digit ZIP Codes, the United States and such subareas as
regions, divisions, states, and counties, and a file presenting data
for congressional districts. Summary Tape File 4, in three files, will
provide  similar statistics with greater detail on such subjects as
race and ethnicity.

   The Census Bureau also will provide two sets of computer tapes that
contain a sample of responses to individual questionnaires, without
containing any information about the household address or identity of
its residents. These "public use microdata samples," or PUMS, are of
great interest principally to academic researchers who do their own
tabulations in order to study some characteristics in more detail. To
further protect the confidentiality of individual records, these files
will be available only for areas with at least 100,000 residents. Two
sets of PUMS are planned: a 5-percent sample in geographic areas that
meet the 100,000 population minimum requirement, and a 1-percent
sample in metropolitan areas.


Printed Reports

   Census Bureau printed reports follow an organization similar to that
of the summary tape files from which they are prepared. There are
three series that present, in turn, data for population characteris-
tics alone, for population and housing characteristics together, and
for housing characteristics alone. Some publications report tabu-
lations from the short-form questionnaire and others from the long
form. The information is released on a state-by-state basis, as
individual state tabulations are prepared, with national summaries
released once the state volumes are completed.

   The three series are the 1990 Census of Population (1990 CP), 1990
Census of Population and Housing (1990 CPH), and 1990 Census of Hous-
ing (1990 CH).  Each of these series contains several volumes, with
such titles as "Population and Housing Characteristics for Census
Tracts and Block Numbering Areas" and are also identified by the
state or metropolitan area on which they report. In general, the sub-
ject matter is similar to that published from the 1980 Census. Basic
population and housing data will be published for small geographic
areas, down to the block level, and more detailed data will be pub-
lished for large geographic areas such as states and metropolitan
areas.

   In addition, the Census Bureau plans to publish a series of about
30 population and 10 housing subject reports for the 1990 Census,
dealing with such topics as families and living arrangements, the
elderly, migration, income, recent movers, and other topics of wide-
spread interest. These would contain less geographic detail but much
more subject matter detail on these topics than will be available in
other reports. The information contained in these printed reports
would also be available on computer tape in a series of about 20
Subject Summary Tape Files (SSTFs).

   Finally, the Census Bureau is also considering publishing a report
that provides a broad range of data about the population at the
national, state and metropolitan area levels. This report would be
published as soon as possible in the tabulation and publication sche-
dule to provide the first overall account of the American population
as revealed by the 1990 Census. A similar report followed the 1980
Census.(11)


Obtaining Data

   There are several different ways to obtain census data products.
The U.S. Government Printing Office sells the printed volumes by mail.
Selected volumes are also available in bookstores and Commerce Depart-
ment district offices. Many census reports are available in hundreds
of libraries that have been designated Federal Depository and Census
Depository Libraries. In addition, the Census Bureau's State Data
Centers in every state have copies of printed reports and offer
assistance in obtaining and using census data on computer and
microfiche as well. (They are listed on pages 39-42 together with
addresses of Census Bureau regional office.)

   Computer tapes, microfiche, and prints from microfiche are sold
directly by the Census Bureau through its Data User Services Office.
The Bureau annually publishes the Census Catalog and Guide, which lists
all products available from the Bureau. The Monthly Product Announce-
ment keeps this information up to date. The Census Bureau also plans
to publish a guide on how to obtain useful information from the 1990
Census, similar to the 1980 Census of Population and Housing Users'
Guide.

   "The Bureau will not only continue to seek the most appropriate
media for making its data available, but will also work to promote
their use--through education and training programs, user-support sys-
tems, and seeking new ways to foster awareness of census data and
their value," according to Paul T. Zeisset of the Census Bureau.(12)


Source:"Two Hundred Years And Counting," The Population Reference
        Bureau, Washington, D.C.