Catherine A. Fitch

Building the National Historical Geographic Information System

Abstract The National Historical Geographic Information System (NHGIS) is a new project to make a rich body of aggregate census data accessible within a Geographic Information Systems (GIS) framework for historical population research. The authors are developing a database incorporating all available aggregate census information for the United States between 1790 and 2000, including all surviving machine-readable aggregate data and new data transcribed from printed and manuscript sources. They are also creating new census-tract maps back to 1910, state and county maps back to 1790, and additional maps when feasible. Availability of high-quality boundaries for key statistical areas will permit the reconciliation of changes in census geography. Census data, documentation, and boundary files will be freely disseminated through an integrated Web-based data access and mapping system.

Interoperable and accessible census and survey data from IPUMS

The first version of the Integrated Public Use Microdata Series (IPUMS) was released to users in 1993, and since that time IPUMS has come to stand for interoperable and accessible census and survey data. Initially created to harmonize U.S. census microdata over time, IPUMS now includes microdata from the U.S. and international censuses and from surveys on health, employment, and other topics. IPUMS also provides geo-spatial data, aggregate population data, and environmental data. IPUMS supports ten data products, each disseminating an integrated data collection with a set of tools that make complex data easy to find, access, and use. Key features are record-level integration to create interoperable datasets, user-friendly interfaces, and comprehensive metadata and documentation. The IPUMS philosophy aligns closely with the FAIR principles of findability, accessibility, interoperability, and re-usability. IPUMS data have catalyzed knowledge generation across a wide range of social science and other disciplines, as evidenced by the large volume of publications and other products created by the vast IPUMS user community.

Terra Populus: Integrated Data on Population and Environment

Terra Populus, part of National Science Foundations DataNet initiative, is developing organizational and technical infrastructure to integrate, preserve, and disseminate data describing changes in the human population and environment over time. A large number of high-quality environmental and population datasets are available, but they are widely dispersed, have incompatible or inadequate metadata, and have incompatible geographic identifiers. The new Terra Populus infrastructure enables researchers to identify and merge data from heterogeneous sources to study the relationships between human behavior and the natural world.

Historical Census Record Linkage

For the past 80 years, social scientists have been linking historical censuses across time to study economic and geographic mobility. In recent decades, the quantity of historical census record linkage has exploded, owing largely to the advent of new machine-readable data created by genealogical organizations. Investigators are examining economic and geographic mobility across multiple generations, but also engaging many new topics. Several analysts are exploring the effects of early-life socioeconomic conditions, environmental exposures, or natural disasters on family, health and economic outcomes in later life. Other studies exploit natural experiments to gauge the impact of policy interventions such as social welfare programs and educational reforms. The new data sources have led to a proliferation of record linkage methodology, and some widespread approaches inadvertently introduce errors that can lead to false inferences. A new generation of large-scale shared data infrastructure now in preparation will ameliorate weaknesses of current linkage methods.