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 blocks. Among the important considerations in grouping such small block polygons were the size of adjoining potential census block polygons as well as the type of bounding features. The program attempted to identify, with separate numbers, potential census block polygons that fell within the size range of typical residential blocks.

The program generally produced a serpentine pattern of block numbers beginning in the upper right of each BG (see Figure 11-2). The program was able to skip those polygons that retained their 1980 census block number; this measure ensured intercensal and numeric geographic comparability for those census blocks that had retained the same boundaries. The program assigned all water body polygons within a BG to a single block number ending in 99 (for instance, water in BG 1 was assigned to Census Block 199, water in BG 2 was assigned to Census Block 299) regardless of whether those water polygons were contiguous. The automated delineation resulted in a national total of 6,461,804 collection blocks (6,517,390 including Puerto Rico and the Outlying Areas). Of this total, approximately two million census collection blocks contained zero population based on the results of the 1990 census.

Figure 11-2. Serpentine Pattern of Census Block Numbering Census Blocks and Block Groups11-13