http://tags.library.upenn.edu/tag/research+tract PennTags Feed for /tag/research+tract PennTags Feed http://tags.library.upenn.edu/makerecord/voyager/37266 http://tags.library.upenn.edu/makerecord/voyager/37266 CensusCD neighborhood change database (NCDB) [electronic resource] : 1970-2000 tract data : selected variables for US Census tracts for 1970, 1980, 1990, 2000 and mapping too / Geolytics. <div class="mlacite">ability to see tracts either as they were in prior decades or "normalized" to same boundaries in 2000</div> <p><br /></p>