STATE AND LOCAL GOVERNMENT DEMOGRAPHY

State and local government demography involves the application of demographic concepts, data, and techniques to public-sector problems at the subnational level.

The field is considered part of applied demography, in which demographic data and methods are used to solve real-world problems. (Another closely-related field is business demography: the application of demography to private-sector issues and decisions.) As Hallie J. Kintner and colleagues (1994) and Jacob S. Siegel (2002) explain, applied demographers' work products are used by government agencies, schools, businesses, legal practitioners, and policy makers. State and local government demography, along with the rest of applied demography, tends to be practical rather than theoretical.

This article describes contemporary state and local demographic practice in the United States, where demographic data (mainly from the national census and birth and death records) are fairly current and reasonably accurate. In a few other countries, universal population registers and frequent censuses simplify the work of demographers on subnational geographic units because it is much easier to quantify migration. In many other countries, there are fewer sources of reliable and current data on such sub-national units.

The scope of the field continues to broaden, however, as additional data sources, analytical tools, and data processing technology are developed. The lag time associated with data collection has shortened markedly–suggesting the eventual possibility of almost "real time" population estimates. Increasingly, the results of state and local demographers' work are available to potential users through the Internet.

Fundamentals of State and Local Demography

The core activity in this field is small-area population estimation. State and local agencies often engage individuals with demographic training to do this work, some contract with academic consultants, and some purchase estimates for small geographic areas from commercial data vendors. Regardless of the source, these estimates are the foundation of state and local demographic work. In addition to population estimates, state and local demographers also provide population forecasts for states and smaller geographic areas.

Data used for state and local population estimates include national and sub-national censuses, administrative records, and other surveys. Periodic census results provide a check of the quality of the procedures used in deriving those estimates. Recent U.S. censuses have included extensive data on population characteristics and information (much of it on a sample basis) on housing and various socioeconomic measures. Census data releases reflect imposition of stringent restrictions protecting individuals's privacy, but allow detailed cross-tabulations and provide some data for areas as small as a single city block.

Administrative records consist of federal, state, and local governmental data gathered for purposes of registration, licensing, regulation, and program administration (e.g., Stanley K. Smith, et al. 2001). They include vital statistics (births, deaths, marriages, divorces); measures of income and poverty; some information on health, employment, and housing; school enrollment data; and records of other activities that are registered or known to the government.

Sample survey data are also sometimes used in state and local demography. In the United States, the Current Population Survey (for larger geographic entities) and the American Community Survey are important sources of such data. State and local government agencies (such as public health departments, housing agencies, and school systems) sometimes conduct special-purpose sample surveys.

Several methods are commonly used to make small-area population estimates. Stanley K. Smith and colleagues describe these methods in detail. The simplest involves multiplying the number of housing units in the area of interest by the average number of persons per household, and adding the estimated numbers in group quarters and the homeless population. The number of housing units can be derived from administrative records like building permits, utility customers, and property tax records. Persons per household can be estimated in a variety of ways, but is typically calculated from census data. This is called the housing unit method.

The component method of population estimation starts with the area's base population (often the latest census count) and adjusts it for the subsequent numbers of births, deaths, in-migrants, and outmigrants. Vital statistics provide birth and death data. Migration is estimated using a combination of administrative records, which may include data from income tax returns, public health insurance membership (in the United States, Medicare), school enrollments, driver's license applications and address changes, and international immigration records. The method can be used to provide separate estimates by age, sex, race or ethnicity, and other characteristics.

Demographers also use regression methods to adjust base populations for current small-area estimates. Regression models may incorporate data on vital events (births and deaths), school enrollment, utility customers, building permits, voter registration, driver's license applications and address changes, tax returns, and other data from administrative records as independent variables. A variety of such models have been developed and applied by the U.S. Census Bureau and similar organizations.

State and local demographers use small units of geographic analysis. These include individual real estate parcels or street addresses, neighborhoods, census divisions (city blocks, block groups, tracts, places, counties, groups of counties), postal codes, special administrative districts (school, water, hospital, sanitation, etc.), public health regions, traffic zones, and political entities like city council and state legislative districts. Population estimates tend to be more accurate for larger geographical areas and those that have relatively stable populations; greater uncertainty attaches to population estimates for smaller geographical units and those that have unstable demographic processes.

State and local demographers increasingly make use of geographic information systems (GIS) software in addition to statistical and database software. GIS can link all types of data to relevant geographical features and thus facilitate the spatial analysis and mapping that are essential to understanding regional variation in many variables of interest. GIS software uses an electronic base map of a region (such as the U.S. Census Bureau's TIGER) identifying roads, political boundaries, census geography, and other manmade and natural geographical features. Each type of feature may be depicted as a separate region, line, or point layer that can be turned on or off as needed. Databases can be linked to each layer. Individual data records with street addresses can be geocoded (assigned latitude and longitude coordinates, or electronically pin-mapped) and aggregated by the enclosing regions. Satellite and aerial photographic images can also be incorporated into a GIS database. The software allows data associated with any type of feature to be aggregated, disaggregated, transferred to other layers, and analyzed.

Many U.S. states have official state demographers, as well as web sites with extensive offerings of data and reports that can be viewed online and downloaded. For example, the California Department of Finance's Demographic Research Unit has posted population estimates (historical and current), projections, and research papers on its web site. Many states' web sites offer census data for the state and its political subdivisions.

Some cities and regional government councils or associations also have web sites containing census and other specialized demographic data (see, for example, the site of the San Diego Association of Governments). Data sometimes include estimates and forecasts of employment, economic conditions, household numbers, and housing, as well as other demographic information. Universities sometimes perform these services for states and smaller jurisdictions (for example, the Bureau of Economic and Business Research (BEBR) at the University of Florida web site).

Applications of State and Local Government Demographic Analysis

The work of state and local government demographers is used by urban, rural, and regional planners, as well as by public organizations and businesses. Fields of application include housing, public health, education, law enforcement, traffic control, environmental impact analysis, disaster planning, and electoral redistricting.

Housing. Demographers can track housing stock at the local and regional levels using permit data on building construction and demolition, utility hookups, and property tax records. Data on housing numbers and characteristics are used to target areas for redevelopment and for the location of public housing, subsidized housing, and housing for the elderly. Housing data by age and race or ethnicity are used to identify possible housing discrimination. Database software makes it simple to connect housing data from administrative records (such as property tax rolls) with population characteristics. GIS software permits mapping and visualization of geographical variation.

Public health. Public health agencies use state and local demographic data to develop community health indicators, analyze population health in terms of outcomes as well as social and environmental determinants, locate clinics and health services, and for disease surveillance. Epidemiologists need population estimates for calculation of fertility, morbidity, mortality, and other rates, which are often calculated by age, sex, race or ethnicity, and other demographic variables. Health maintenance organizations, hospitals, and health insurers also use demographic data. Su-Lin Wilkinson and colleagues (1999), and Jeanne G. Gobalet and Richard K. Thomas (1996) give examples of demographic techniques used in the public health field. The work of Louis G. Pol and Richard K. Thomas (2001) provides an extensive discussion of health and health care demography.

School enrollment. State and local government demographers help public schools forecast enrollments. They make projections of future student body size by grade using past data on grade progression rates and information on births five years earlier (to forecast kindergarten enrollments). Alternatively, or additionally, future enrollments can be gauged from housing data.

Demographic data are an important input to educational planning: in siting schools, deciding on school closure, realignment of internal attendance area boundaries, and design of desegregation strategies. GIS software is particularly useful in these activities.

Law enforcement. Law enforcement agencies use demographic data to compute crime rates and plan enforcement and prevention measures. Demographic data are used to select trial jury members when laws require that juries be representative cross-sections of the community. State and local demographic data are also used for drawing political boundaries that conform to legal requirements. For example, in the United States, most political subdivision boundaries must be evaluated after each national census and redrawn, if necessary, to achieve population equality across the subdivisions. Civil rights laws also require that political subdivision boundaries permit protected minority group members the opportunity to elect representatives of their choice. State and local government demographers sometimes provide technical support for political redistricting.

Accident patterns and disaster response. State and local government agencies use demographic data to understand traffic accident patterns, to assess environmental impacts, and in planning for major natural disasters. For example, Stanley K. Smith (1996) and the California Department of Finance (1995) have analyzed the effects of hurricanes, earthquakes, and other natural disasters. Programs are developed to assist particular at-risk populations, such as the elderly, poor children, substance abusers, and school dropouts on the basis of local-area demographic characteristics.

Sharing Demographic Data

The Population Association of America's Committee on Applied Demography facilitates interaction among state and local government demographers. The Census Bureau's Federal State Cooperative for Population Estimates and Federal State Cooperative for Population Projections, and the State Data Centers provide a forum for sharing census data with state and local agencies. A significant share of state and local demographers' work entails making national census and other types of demographic, social, and economic data accessible to the public. This sub-area of demographic practice is likely to grow rapidly for the foreseeable future.

See also: Business Demography; Census; Geographic Information Systems; Population Registers; Small-Area Analysis.

bibliography

Gobalet, Jeanne G., and R. K. Thomas. 1996. "Demographic Data and Geographic Information Systems for Decision Making: The Case of Public Health." Population Research and Policy Review 15: 537–548.

Kintner, Hallie J., Thomas W. Merrick, Peter A. Morrison, and Paul R. Voss, eds. 1994. Demographics: A Casebook for Business and Government. Boulder, CO: Westview Press.

Myers, Dowell. 1992. Analysis with Local Census Data: Portraits of Change. New York: Academic Press.

Pol, Louis G., and Richard K. Thomas. 2001. The Demography of Health and Health Care, 2nd edition. New York: Kluwer Academic/Plenum Publishers.

Siegel, Jacob S. 2001. Applied Demography: Applications to Business, Government, Law and Public Policy. San Diego: Academic Press.

Smith, S. K. 1996. "Demography of Disaster: Population Estimates after Hurricane Andrew." Population Research and Policy Review 15: 459–477.

Smith, Stanley K., Jeff Tayman, and David A. Swanson. 2001. State and Local Population Projections: Methodology and Analysis. New York: Kluwer Academic/Plenum Publishers.

Wilkinson, S. L., Jeanne G. Gobalet, M. Majoros, B. Zebrowski, and G. S. Olivas. 1999. "Lead Hot Zones and Childhood Lead Poisoning Cases, Santa Clara County, California, 1995." Journal of Public Health Management and Practice 5(2): 11–12.

internet resources.

Bureau of Economic and Business Research (BEBR) at the University of Florida Website. <http://www.bebr.ufl.edu>.

California Department of Finance's Demographic Research Unit. <http://www.dof.ca.gov>.

Hoag, Elizabeth, and California Department of Finance. 1995. "The Effect of the Loma Prieta Earthquake on California Migration." <http://www.dof.ca.gov/HTML/DEMOGRAP/Disaster.pdf>.

San Diego Association of Governments. <http://www.sandag.org>.

Jeanne Gobalet