TIGER/Line Shapefile, 2014, Series Information File for the Current Block Group State-based Shapefile

block groups bgs are clusters of blocks within the same census tract each census tract contains at least one bg and bgs are uniquely numbered within census tracts bgs have a valid code range of 0 through 9 bgs have the same first digit of their 4 digit census block number from the same decennial census for example tabulation blocks numbered 3001 3002 3003 3999 within census tract 1210 02 are also within bg 3 within that census tract bgs coded 0 are intended to only include water area no land area and they are generally in territorial seas coastal water and great lakes water areas block groups generally contain between 600 and 3 000 people a bg usually covers a contiguous area but never crosses county or census tract boundaries they may however cross the boundaries of other geographic entities like county subdivisions places urban areas voting districts congressional districts and american indian alaska native native hawaiian areas the bg boundaries in this release are those that were delineated as part of the census bureau s participant statistical areas program psap for the 2010 census