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By maintaining separate sets of block numbers for collection and tabulation, we can renumber blocks for tabulation to recognize changes to the feature pattern; we also can eliminate situations that resulted in the creation of "sliver" census tracts for the 1990 census. The introduction of an independent numbering cycle for tabulation will allow us to assign additional block numbers to blocks formed by new features that were discovered during our enumeration activities. In addition, the use of separate block sets for collection and tabulation will enable us to better serve the participants in our statistical area programs (such as those programs for census tracts, block groups, and census designated places), and provide an opportunity for our local participants in these programs to verify the plans they submit for these areas. Boundaries defined by local participants for statistical areas will better reflect the most recent feature changes to fast-growing areas.
Because census blocks provide a statistical framework for a variety of Federal, state, and local programs designed for such purposes as transportation planning or providing rural services, persons served by these programs will benefit as well. These changes allow the Census Bureau to associate water polygons with a surrounding land block (for both collection and tabulation operations), thereby allowing individuals preparing equivalency files to make a more precise assignment of water.
The Census Bureau has produced Census 2000 Block Relationship Files on the basis of one-to-one, one-to-many and many-to-one block(s). The purpose of the relationship files is to show how 1990 census blocks now relate to Census 2000 blocks. The relationship files contain a part flag field. A value of "p" in this field identifies blocks that do not have a whole block to whole block relationship. They do not depict the actual spatial relationships between census blocks. The actual areal relationships between blocks can be determined using commercially available GIS software and publicly available versions of the Census Bureau’s TIGER/Line files.
The Census Bureau organized its address list for review by tribal and local government liaisons before Census 2000 (under Public Law 103-430) using the collection block numbers; we provided the 1990 tabulation block number for each address in addition to the collection block numbers. The Census Bureau is confident that these changes relating to block numbers and the separation of collection geography from tabulation geography will provide an improved and more accurate geographic data base, and that the relationship files described above will facilitate operations for local participants in our Census programs.