Compiled with assistance from Hugh Calkins, State University
of New York at Buffalo
NOTES
It may be useful to illustrate this unit with several
different examples of the data products described, including
examples of census products such as summary reports, maps and
even digital tapes.
UNIT 8 - SOCIO-ECONOMIC DATA
Compiled with assistance from Hugh Calkins, State University
of New York at Buffalo
A. INTRODUCTION
Socio-economic data
- are data about humans, human activities, and the space
and/or structures used to conduct human activities
- specific classes include
- demographics (age, sex, ethnic and marital status,
education)
- housing (quality, cost)
- migration
- transportation
- economics (personal incomes, employment,
occupations, industry, regional growth)
- retailing (customer locations, store sites, mailing
lists)
Aggregate and disaggregate data
- disaggregated data - data about individuals or single
entities, for example:
- a person's age, sex, level of education, income,
occupation, etc.
- gross sales, number of employees, profit, etc. for a
retail store
- registration number and type for a single vehicle
- aggregated data - describing a group of observations with
the grouping made on a defined criterion
- geographical data are often grouped by spatial units
such as a census tract, traffic zone, etc.
- aggregation can also be by time interval
- e.g. number of persons leaving area in 5 years
- also by socio-economic grouping
- e.g. persons aged 5 through 14 years
- examples of aggregated data are:
- number of persons, average income, median
housing value for a census tract
- number of commute trips and average trip length
from a suburban traffic zone to the central
business district
Cross-sectional and longitudinal data
- recall from Unit 6
- cross-sectional data gives information on many areas
for the same single slice or interval of time
- e.g. average income in census tracts of Los
Angeles for 1988
- e.g. numbers migrating out of each state in the
period 1971-75
- longitudinal data gives information on one or more
areas for a series of times
- e.g. average income for State of New York from
1970-1988 by year
B. SOCIO-ECONOMIC DATA FOR GIS
Sources of socio-economic data
- field surveys
- much data used in marketing is gathered by door-to-
door or street interview
- field surveys require careful sampling design
- how to obtain a representative sample
- how to avoid bias toward certain groups in
street interviews
- government statistics
- statistics collected and reported by government as
part of required activities, e.g. Bureau of the
Census
- usually based on entire population, except sampling
is used for some Census questions
- government administrative records
- records are collected by government as part of
administrative functions, e.g. tax records, auto
registrations, property taxes
- these are useful sources of data provided
confidentiality can be preserved
- usually available only to government or for research
purposes
- secondary data collected by another group, often for
different purposes
- e.g. the original mandated purpose of the Census was
to provide data for congressional districting
- increasingly socio-economic data is available in digital
form from private sector companies
- retailers and direct-mail companies are major
clients for these companies
- includes data originally from census augmented from
other sources and surveys
- data can be customized for clients (special sets of
variables, special geographical coverage or
aggregation)
- customizing justifies costs, which are often higher
than for "raw" census data
"Geography"
- for use in GIS, socio-economic statistics are of little
use without associated "geography," the term often used
to describe locational data
- e.g. data on census tracts must be supported by
digital information on locations of census tract
boundaries
- geography also allows data to be aggregated
geographically, e.g. by merging data on individual cities
into metropolitan regions
- thus, many suppliers of socio-economic data also supply
digitized geography of reporting zones
- boundaries of many standard types of reporting zones
change from time to time
- e.g. changes occur occasionally in county boundaries
- e.g. census enumeration districts are redefined for
each census (see Redistricting in Unit 56)
- difficult to assemble longitudinal data for such
units due to changing geography
- data is often needed for one set of reporting zones, only
available for another set
- e.g. data available for census tracts, required for
school districts which do not follow same boundaries
- such problems of cross-area estimation are
facilitated by GIS technology
- these problems are often grouped into the area of
modifiable area problems (MAP)
- considerable effort has been expended recently to
develop statistically sound techniques to deal with
these problems (see Openshaw, 1981)
Issues in using secondary socio-economic data
- cost
- usually secondary data is much less expensive than
field surveys
- large expenditures by government agencies on data
collection (e.g. US Census) are indirect subsidies
to users, who often pay much less than real cost of
data
- documentation
- quality of documentation, supporting information
(e.g. maps) is usually high for data collected by
government
- data quality
- major difficulty is undercounting - census and other
social surveys tend to miss certain groups, leading
to bias in results
- undercounting in US Census may be as high as 25% for
certain social groups
- data conversion
- conversion steps may be necessary to make data
useful in GIS
- e.g. format, type of data may be incompatible
- aggregation
- are data available with suitable level of spatial,
temporal aggregation?
- e.g. study to change elementary school district
boundaries will require data at resolution of
city blocks or higher
- e.g. location for gas station will require city
block level data, for regional shopping mall
much lower resolution (greater aggregation of
data) is adequate
- currency
- social data changes rapidly, can be quickly out of
date because of births, deaths, migration, changing
economy
- competitive edge in retailing depends on having
current data
- US has a major census only every 10 years, so its
data may be 10 years old
- often have to estimate current or future patterns
based on old data
- accuracy of location
- census locates people by place of residence -
"night-time" census
- "daytime" data would show locations during the day
(place of work, school etc.) but is generally not
available from standard sources
- medical records often locate individuals by place of
treatment (hospital), not residence or workplace
- e.g. consider implications for detecting
exposure to cancer-causing agents
C. SOURCES OF SOCIO-ECONOMIC DATA
Population census
- questions on age, sex, income, education, ethnicity,
migration, housing quality etc.
- summary statistics used in research, planning, market
research, available at high level of geographic
resolution in many countries
- see detailed discussion following for US case (Census of
Population and Housing)
Economic census
- enumeration and tabulation of business activity is
conducted in the US by the Census Bureau in years ending
in 2 and 7
- detailed information on classes of industry
- low level of geographic resolution (i.e. large reporting
zones)
- data collected in many countries through annual,
quarterly or monthly returns of information from
companies
Agricultural census
- annual data on crops, yields, livestock etc.
- more extensive periodic surveys of farm economy
- available in spatially disaggregated form to e.g. county
level in US
Labor force statistics
- enumeration of employment, unemployment
- produced from periodic (e.g. monthly) sample surveys of
workforce
- other special-purpose surveys often combined with regular
labor force survey - e.g. household expenditures,
recreation activities
- often available for small areas, e.g. parts of city
Land records
- record of land parcel description, ownership and value
for taxation purposes
- updated on a regular basis (e.g. annually) by
municipality or county government
- also used for land use planning
- source of current demographic information in some
countries/states (i.e. local census)
- see detailed discussion following
Transportation and infrastructure inventories
- planning, management and maintenance of facilities
- includes roads and streets, power lines, gas lines,
water, sewer lines
- collected by local utilities, responsible government
departments
- valuable to variety of users
- e.g. construction companies needing information on
buried pipes
- e.g. emergency management departments needing data
on hazardous facilities
- compiling agency often sees a substantial market for such
data which can offset costs of collection
Administrative records
- vehicle registrations, tax returns etc.
- useful for various marketing, research purposes
- based on 100% sample so can be disaggregated spatially
- however, disaggregation causes problems over
confidentiality of records
D. US CENSUS OF POPULATION AND HOUSING
Process of taking the census
- purpose is to enumerate the population for redefining
election districts
- taken every ten years (l960, l970, etc.)
- April lst is census day, although complete enumeration
takes a "few" weeks
- most households receive forms in mail, some require visit
by enumerator
Content
- two types of items - those completed by "100%" of the
population, those by random sample
Processing of returns
- automated encoding to digital form
- automated editing to correct obvious inconsistencies
- some missing items can be assigned automatically using
simple rules
- other missing items are assigned based on probabilities
- data assembled into master database
- sample surveys processed to produce statistical summaries
Geographic referencing
- initially returns are identified by street address
- address is converted into geographic location using a
digital referencing system
- for the 1980 census, DIME (Dual Independent Map
Encoding) files were used for digital geographic
referencing of urbanized portions of the US
- for the 1990 census, TIGER files covering every
county will be used
- since TIGER files will have a major impact on GIS
databases in the next decade, they are discussed in
detail in the next section
Census reporting zones
- range from blocks to states
- as noted previously, the geographic boundaries and
definitions of these areas may change from one census to
the next
Availability of Census data
- tabulation of statistics by reporting zones, e.g.
population by county, population by age by county
- crosstabulation, e.g. population by age and sex by county
- special tabulations, e.g. for unusual combinations of
characteristics, or for unusual or custom reporting zones
- number of possible tabulations and crosstabulations is
infinite, volume of census products vastly exceeds volume
of data collected
- alternative formats for products
- printed reports
- magnetic media - tapes, disks
- microfiche, microfilm, now CDs
- sources of census data
- state data centers distribute Census data
- private firms repackage and customize data, produce
custom reports (e.g. tabulation of population by
distance from proposed mall location)
- geography products available
- base maps showing reporting zones
- atlases produced for urban areas
- digital products - boundary files, TIGER
E. TIGER
- reference: beginning of this Unit (TIGER)
Development
- TIGER stands for Topologically Integrated Geographic
Encoding and Referencing
- designed to:
- support pre-census geographic and cartographic
functions in preparation for the 1990 Census
- to complete and evaluate the data collection
operations of the census
- to assist in the analysis of the data as well as to
produce new cartographic products
- TIGER files were created by the Bureau of the Census with
the assistance of the US Geological Survey
Content
- TIGER/line files are organized by county
- they contain:
- map features such as roads, railroads and rivers
- census statistical area boundaries
- political boundaries
- in metropolitan areas, address ranges and ZIP codes
for streets
Marketing TIGER files
- Census Bureau
- 1990 Census versions of TIGER/Line files will be
available from the Census Bureau in early 1991
- cost for prototype and precensus TIGER/Line
files on magnetic tape are $200 (US) for the
first county and $25 for each additional county
in that state ordered at the same time
- the 50 states plus DC on tape cost $87,450
- precensus files are also available on CD-ROM for
$250 per disk, 40 disks are required for coverage of
the entire country (all prices as of Jan. 1990)
- Third party vendors
- as of December 1989, 25 vendors had notified the
Census Bureau that they will market repackaged
versions of TIGER/Line files, in many cases with
software which will enable users to access this data
easily and quickly
- many of these products are being designed for use on
micro-computers
Non-census uses for TIGER
- TIGER files are valuable for other purposes
- e.g. locating customers from address lists
- e.g. planning vehicle routes through city streets,
for parcel delivery, cab dispatching
- for these purposes TIGER files need to be kept
current at all times, but Bureau of the Census only
requires them to be current every 10 years
- see Unit 29 for technical details of TIGER files
F. LAND RECORDS
- many systems have been developed by local governments in
the US to manage land, particularly in urban areas
- in other countries there has been more effective
coordination at provincial and national levels, e.g.
Australia
- practices in different countries depend on the
system of land tenure
- the basic entity in land records systems is the land
parcel, i.e. the basic unit of ownership
- traditionally, land records have been managed by hand
using methods which often date back 200 years
- land records are the basis of the system of local
taxation, administration, as well as transfer of
ownership and subdivision
Issues in land records modernization
REFERENCES
The Bureau of the Census, US Department of Commerce produces
numerous documents on the Census and its products,
including TIGER. Factfinder for the Nation describes
data available from the Census Bureau. Census '90 Basics
describe the content, geographic areas and products of
the census. Similar material is available from
appropriate organizations in other countries, e.g.
Statistics Canada.
Marx, R. W., ed, 1990. "The Census Bureau's TIGER System," a
special issue of Cartography and Geographic Information
Systems Vol 17(1). Contains several articles providing
details on the contents and database structure of TIGER.
Kaplan, C.P. and T.L. van Valey, 1980. CENSUS '80:
Continuing the Factfinder Tradition, US Department of
Commerce, Bureau of the Census. A good review of Census
applications.
Richards, D. and P.M. Jones, 1984. "General sources of
information," in R.L. Davies and D.S. Rogers, eds., Store
Location and Store Assessment Research, John Wiley and
Sons, New York, Chapter 4. This chapter reviews sources
of socio-economic data in both the US and the UK.
Marx, R.W., 1986. "The TIGER System: Automating the
Geographic Structure of the United States Census,"
Government Publications Review 13:181-201. Discusses the
development of the TIGER system
Openshaw, S., 1977. "A geographical solution to scale and
aggregation problems in region-building, partitioning and
spatial modelling," Institute of British Geographers,
Transactions 2(NS):459-72.
Openshaw, S., and P.J. Taylor, 1981. "The modifiable areal
unit problem," in N. Wrigley and R.J. Bennett, editors,
Quantitative Geography: A British View, Routledge,
London.
EXAM AND DISCUSSION QUESTIONS
1. Confidentiality is a major issue in the US Census, and
the need to preserve privacy conflicts directly with the
need for disaggregated data for numerous purposes. What are
the factors to be considered in trying to reconcile these
conflicting needs? Is the balance affected by use of GIS?
2. Devise a scheme for creating and maintaining a constantly
updated digital file of all streets and associated address
ranges etc., i.e. a perpetually current TIGER. What would
be the costs of the scheme, and what advantages would it
have over the current situation?
3. "The concept of a decennial census was devised almost two
hundred years ago and has become increasingly inappropriate
to the modern age". Discuss.
4. A spreadsheet (such as Lotus 1-2-3) allows the user to
perform a variety of functions on tabular data. Discuss the
possibility of a "geographical spreadsheet" - what would it
do, and what applications would it have it?
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