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In 2010 the U.S. Census Bureau changed some of the boundaries defining different census geographies. Some data aggregators, including SimplyMap, allow you to show some of the variables in either the 2000 or 2010 geography. You can get the Geographic Comparability File for the 2010 to 2000 Places here. If you are comparing between the 2000 and 2010 Census data you might want to take a look at where the significant changes are.
Counties (or Statistically Equivalent Entities) are legal divisions within states. These are not uniform and have changed over time. For example, the Census Bureau still uses the counties for Connecticut even though they have been dissolved as legal entities.
Please click on the title to see exceptions and historical issues for specific states.
All information in this section is from the U.S. Census Bureau website in their Geography pages under Terms & Concepts. Please click on the heading for the source webpage.
Size Range: 1200-8000 people Optimal Size: 4000 people Boundaries: Mostly related to existing boundaries Numbers: Up to 4 digits with an optional 2 digit suffix after a decimal (ex. 1457.02, 23) Codes: 6 digits, the last 2 representing the digits after the decimal (ex. 145702, 002300)
Before using Census data based on Zip Code Tabulation Areas, please read the documentation provided on the U.S. Census Bureau website. Remember that Zip Codes assigned by the USPS change over time, and the ZCTAs don't always reflect that.
From the U.S. Census website: "The Census Bureau defines ZCTAs by allocating each block that contains addresses to a single ZCTA, usually to the ZCTA that reflects the most frequently occurring ZIP Code for the addresses within that tabulation block. Blocks that do not contain addresses but are completely surrounded by a single ZCTA (enclaves) are assigned to the surrounding ZCTA; those surrounded by multiple ZCTAs will be added to a single ZCTA based on limited buffering performed between multiple ZCTAs."