Relationship Files
Contents
Census relationship files are a set of geographic data files provided by the U.S. Census Bureau that describe the relationships between different types of geographic entities. They are essential for anyone who needs to compare data across different geographic boundaries or over time.
There are two main types of relationship files:
| 1. | Geographic Relationships Between Entity Types: These files show how different types of geographic areas relate to each other for the same time period. For example, a relationship file might show how census tracts relate to congressional districts, or how places (cities and towns) relate to ZIP Code Tabulation Areas (ZCTAs). These files are crucial for answering questions like: "Which congressional districts are located within this particular county?" or "What parts of this city are in each state legislative district?" |
| 2. | Geographic Relationships Over Time (Comparability): These files show how the same type of geography has changed between different census years. Since geographic boundaries can be redrawn every decade, it can be difficult to compare data from the 2010 Census to the 2020 Census. These relationship files, for instance, a "2020 Block to 2010 Block Relationship File," help users understand how blocks, tracts, or other areas from a previous census year correspond to the new boundaries in the latest census. They often include information on the area of overlap between the old and new boundaries, which is useful for creating population estimates for the new areas. |
In contrast to equivalence files, which primarily link census blocks to political districts for the purpose of redistricting, relationship files are a broader category of tools. They are used for a wider range of data analysis and are vital for understanding the complex and dynamic nature of U.S. census geography.