Social Explorer is the only data provider that quickly and easily allows you to compare results of the 2010 Census to the latest version — even down to the block group level, which includes roughly 240,000 untis in the United States, as well as places, county divisions, counties and other Census areas.

There are two caveats. First, geographic boundaries for places and counties may change over a decade, due to political factors such as annexation and redawaing, as well as changes in the mapping process.. Likewise, the Census Bureau redrasws all of its "census geographies" including blocks, block groups, and tracts. Using a very detailed file that documents  all block level changes between the 2010 and 2020 Census, Social Explorer allocated the block data from 2010 to 2020 based upon land area.  This could inject some minor errors into the data.

Second, the Census Bureau used a new Disclosure Avoidance System  that in effect shifted individuals and their characteristics from one Census block to another,, resulting in false information being presented, i.e., areas being composed entirely of people younger than 18 years old, or neighborhoods of exclusively one race that don't exist. For this reason, Social Explorer recommends extreme caution when making comparisons at very small geographic levels, especially among  block groups, and tracts, and places, counties and county divisions with very small populations.  At this writing we have not  included the block data because the Census has confirmed that the block data are in effect filled with errors due to this procedure.  However, for large geographies the errors in effect cancel out, so that they data do represent the information that was collected by the Bureau.

Author: Frank Bass