Estimating Congressional District Data


The legislative branch of the U.S. government is composed of Senators, with two from each state, and 436 U.S. House of Representative members, representing areas across the nation referred to as Congressional Districts. IMPLAN’s Congressional District (CD) data are aggregations of the IMPLAN zip code data.


Substantial redistricting happens after each Decennial Census, with minor changes possible between Census years. When such changes occur, the Census Bureau publishes a new correspondence file relating existing Zip Code Tabulation Areas (ZCTAs) to the new set of Congressional Districts (CDs) on its Relationship Files webpage. The changes are incorporated into all subsequent IMPLAN CD data sets.

The Census Bureau’s relationship files do not include point zip codes; thus, we must assign point zip codes to CDs based on other publicly available information about those point zip codes.

When a ZCTA falls across more than one CD, it is divided equally among the corresponding CDs. For more information on how zip codes are tabulated in IMPLAN, check out the article Estimating Zip Code Data. The main thing to note is that since zip codes appear and disappear every year, IMPLAN creates a new bridge between Zip Codes and CDs every year. When a new CD is added by Congress, we incorporate that new CD into the dataset. You can find the crosswalk between zip codes and CDs in the article U.S. 546 Industries, Conversions, & Bridges.



Written April 18, 2024