Understanding how neighborhoods change over time is fundamental to addressing the problems and opportunities of America's communities. Many people are not aware, however, that data obtainable from the U.S. Bureau of the Census cannot be used directly for these purposes, because of many changes in census tract boundaries and variable definitions between census years. In the early 1990s, with funding from the Rockefeller Foundation, the Urban Institute made adjustments as necessary to create the first national data file with consistently defined tract level census data for 1970, 1980 and 1990. That file has since been used as the basis for important research on how the nation's communities changed over those decades.

Rockefeller has again provided funding to allow the Urban Institute to add 2000 census data to the file. To do so, the Institute has collaborated with GeoLytics, to not only add 2000 data but also to transform the product to make it much more user friendly and technically superior to the earlier version in a number of respects. GeoLytics applied their proprietary weighting tables for 1970, 1980, and 1990 to carefully convert past census data to new 2000 tract boundaries. This procedure allows NCDB data to be accurately compared over time for the exact same geographical boundaries.

Another improvement is that the NCDB data products are being released on CD-ROM using GeoLytics' proprietary data compression and mapping technology. The data can be accessed using the menu-driven mapping and analysis software or the data can be extracted for use in external database, mapping, and analysis packages. The collaboration has drawn on the strengths of both organizations, and resulted in a product that is a significant tool for policy-makers, researchers and community practitioners interested in neighborhood change.