Block Groups: Block Group: There are 217,740 Census Block Groups in all the US. Block Groups have the most current and quantifiable data that affects future real estate prices. Block Groups are defined by the US government, and contain approximately 600 households. The Block Group is the smallest geographical unit for which there is reliable data available.

Block Groups are identified by a series of unique numbers. Blocks never cross the boundaries of states, counties, or major roads or rail road tracks, thus typically define the “right side” and the “wrong side” of the rail road tracts. The Block and Tract trends, are the most important areas to consider when investing or properly assessing risk.