Making Sense of the Census

Unlocking the potential of two centuries of data collection

Understanding of many hot-button issues of this century--war and terrorism, political and religious divisions, environmental degradation, social and economic inequalities--begins with demographic data. For years, social science researchers, educators, business managers, government officials, journalists, and others have relied on census data to examine growth and change in American populations and to shed light on the associated cultural, social, and economic issues.

They have used aggregate data tables to describe characteristics of states, municipalities, and neighborhoods. They have taken snapshots of populations and noted shifts and trends. But they have been limited in their ability to access, analyze, and d r aw conclusions from the data.

At the turn of the century, massive amounts of data covering the period 1790 through 2000 existed, but the data were scattered across dozens of archives and stored in incompatible formats in different media. Only a small fraction of the data was available on the Internet. High-quality census boundary files existed for only the 1990 census. To study change, researchers had to develop their own maps at great expense.

The challenge: to unlock the potential of two centuries of data collection and make the information broadly accessible not only to researchers but also to students and the public. This would be a project of unprecedented magnitude. Skeptics said it would be too big, too complicated, and too costly. Enter the University of Minnesota.

The project takes off

The University of Minnesota Population Center had already developed the most powerful and widely used tool for access to census microdata (individual census records), the Integrated Public Use Microdata Series (IPUMS). The geography department, with its Geographic Information System (GIS) expertise, was an ideal partner in the project. An idea took shape, then a proposal.

In 2001 the University applied for and received a $4.8 million, five-year grant from the National Science Foundation to develop the National Historical Geographic Information System (NHGIS). Thus began a project that would cull and organize 750 gigabytes of data from over a million separate source files to create what is being called a priceless data archive--a comprehensive, accessible, high-precision database of U.S. summary data on population, housing, agriculture, manufacturing, business climate, voting patterns, and other georeferenced statistics.

The system is an enormous boon to social science researchers, as well as students, public officials, and the merely curious. It can yield up data to advance understanding of everything from immigrant and ethnic settlement patterns to patterns of residential segregation; from the decline and renaissance of central cities to suburbanization and urban sprawl, rural depopulation and agricultural consolidation; from changes in ecosystems to issues related to transportation, public health and epidemiology, electoral politics, and criminal justice.

"The database opens a new range of powerful approaches to familiar problems, broadening the scope of local and regional analysis and exploring variations across time and space simultaneously," says geography department chair Robert McMaster. "All users, from high school students to research scientists, will be able to adopt comparative and historical perspectives."

Taking the measure of communities

Want to know how immigration has changed your community? Or how your community's housing stock, health, or voter participation have changed over the past 50 years? Or how your city's ethnic makeup or income distribution compares to those of Sacramento, El Paso, or Queens? NHGIS puts such information at your fingertips.

Data that previously required archival specialists to spend days digging (if the data were available at all) are now available at Small data files pop up instantly; large files take no more than a few minutes.

Suppose you want to study residential segregation and urban racial and ethnic change across comparable cities within regions or across the nation. Most segregation studies over the past 40 years focused mostly on a single moment in time or on short-term change. Gathering complex data sets across census years or tracts was just too labor intensive .

NHGIS opens news avenues for studying these patterns. Researchers can now study trends such as changing residence patterns rather than relying on simple snapshots of segregation at a given time. By linking individual census records to tract-level data over time, analysts can even assess how neighborhood change is associated with individual behavior (such as movement between neighborhoods), or study how neighborhood characteristics affect and are affected by the presence of businesses. (A case in point might be the proliferation of restaurants along the stretch of Nicollet Avenue in Minneapolis now known as "Eat Street.")

Or suppose that you're interested in the impact of AIDS or the incidence of certain cancers in your community--and the associated mortality rates among different populations. Such epidemiologic understanding can be gleaned from census data that allow you to trace disease patterns and assess the disparate effects on neighborhood subpopulations over time. And the results of such analysis can form the basis not only for good individual decision making (about where to live, for example) but also for good public policy (public health alerts and interventions, or environmental cleanup).

A new educational toolbox

Through Social Explorer--based at Queens College of the City University of New York ( is bringing the excitement of discovery into secondary school classrooms as well as to a wide range of college courses, from geography to ecology. Designed for students and teachers, Social Explorer features an online historical mapping feature to display demographic changes since 1790. Using the system, teachers can design animated maps showing historical changes, conduct exercises using the data, and generate new understanding of populations trends.

Not for academics only

NHGIS has been warmly received by journalists, community planners, and the private sector. News organizations are able to provide audiences with local statistics and thematic maps displaying thousands of numbers in a single image. Planners use local area statistics as an essential tool for decisions on education, transportation, care of the aged, and other community planning issues. And small businesses, as well as large firms, rely on small-area census data to conduct market research.

"Because NHGIS offers the opportunity to assess demographic and economic trends at the local level, all users will be able to move beyond static analysis and better prepare for the future," McMaster says. "In short, this project not only provides fundamental infrastructure for the social sciences, but also promises to expand the use of such material by the public."

Although the five-year grant is ending, work will continue as the University maintains the database, with a goal of further refining the data access system and expanding the number of data files available within the system. Responding to developments in geographic standards, statistical infrastructure, and information technology, the University has submitted a funding proposal for system upgrades.

Additional funding will support two main tasks. One is to realign NHGIS boundary files to ensure compatibility with new Census Bureau standards and to add geographic levels--including block, congressional district, and zip code areas. The second is to incorporate the American Community Survey, which is replacing the long Census Bureau form.



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This page contains a single entry by cla published on July 23, 2008 11:56 AM.

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