Page:Geographic Areas Reference Manual (GARM).pdf/253

 BNA boundary that the Census Bureau had previously agreed to recognize, and the location shown on the precensus maps. If the census statistical areas committee or the BNA participant notified the Census Bureau of a census tract or BNA boundary discrepancy and requested a correction, the Census Bureau corrected the discrepancy.

Resolving census tract/BNA boundary discrepancies was complicated further by an additional commitment made to data users. Following the 1980 census, many data users complained about two types of geographic inconsistencies that made using the 1980 census data difficult for a majority of data users—duplicate block numbers in a census tract/BNA and block groups consisting of more than one contiguous cluster of blocks (discontiguous block groups). The Census Bureau agreed to correct this for the 1990 census.

When resolving census tract/BNA boundary discrepancies, the Census Bureau expanded the area of a census tract/BNA wherever possible. After expanding the census tract/BNA, Census Bureau staff flagged the census tract/BNA gaining area and the census tract/BNA losing area. This was accomplished by retaining the basic census tract/BNA number of the changed census tracts/BNAs and adding a special two-digit suffix. When assigning the special suffixes, Census Bureau staff began with .98 and assigned subsequent numbers in descending sequence, .97, .96, .95, and so forth (see ).

As a result of the promise not to create discontiguous block groups or duplicate 1990 census block numbers, the Census Bureau did not expand the area of a census tract/BNA if such a revision caused the expanding census tract/BNA to include a census block that was discontiguous with other blocks sharing the same block group identifier, or if resolving the census tract/BNA boundary discrepancy created duplicate 1990 census block numbers. Under these circumstances, the Census Bureau created a separate census tract/BNA composed of the census block(s) in question. The Census Bureau assigned a new census tract/BNA number to the newly created census tract/BNA by retaining the basic number of the 10-10Census Tracts and Block Numbering Areas