Geography is at the center of taking a census. We do not just count people; we count people where they live. Geography is important because it is the basis for taking a census and for tabulating census data. The Census Bureau also maintains unique geographic areas that other local, state and federal agencies use.
Understanding geographic relationships is key to understanding how to properly use Census Bureau data. This is the first in a series of posts that will shed some light on how these different entities relate to one another. Part one focuses on geographic relationships that exist below the national level, such as ZIP Code tabulation areas and school districts.
The Standard Hierarchy of Census Geographic Entities [PDF] displays the relationships between legal, administrative and statistical boundaries maintained by the Census Bureau. It depicts relationships with a line and shows where relationships do not exist by displaying entities on different line tracks. In short, it shows how different geographic areas may, or may not, be related.
Here are some examples to explain how some of the relationships on the hierarchy work.
The hierarchy provides a quick and easy way for data users to see how the different geographic entities at the Census Bureau relate to one another. It is important to understand the hierarchy to get to the correct data. The next Understanding Geographic Relationships post will discuss the hierarchy of geographic entities related to American Indian Areas.
It is the 25 year anniversary of the TIGER (Topologically Integrated Geographic Encoding and Referencing) database. Stay tuned for more on this important milestone in geographic history.