Photo by Blake Wheeler on Unsplash

Occasionally we get asked for ZIP Code-based Census data. We have to say that we don’t have ZIP Code data and neither does the Census. What!? That’s right! But don’t worry, we got your back – the Census publishes ZIP Code Tabulation Areas (ZCTA, pronounced ‘ziktah’).

To quote the Census:

“ZCTAs are generalized area representations of U.S. Postal Service (USPS) ZIP Code service areas. They represent the most frequently occurring five-digit ZIP Code found in a given area. Simply put, each ZCTA is built by aggregating 2010 Census blocks, whose addresses use a given ZIP Code. Each resulting ZCTA is then assigned the most frequently occurring ZIP Code as its ZCTA code.”

In a nutshell: ZCTA 78704 is a representative snapshot of ZIP Code 78704.

ZCTAs Rock! Here’s why:

ZCTAs map to US Census data; ZIP Codes don’t.

About ZIP Codes. We don’t have ZIP code boundaries, because the U.S. Postal Service doesn’t define or publish them. Also, some of ZIP Codes are just routes (a series of connected lines, not polygons).

ZIP Codes change constantly to help the USPS deliver mail more efficiently. That’s what ZIP Codes are designed for: delivery. If you’re planning delivery logistics, use ZIP codes. Some companies offer zip code boundary maps. They estimate (using a variety of methods) polygons based on groups of points, physical landmarks (like bodies of water), and other methods. Most companies have their own private/favorite method of estimating ZIP code boundaries. But because ZIP Codes change so often, boundary maps fall out of sync with US Census demographic data.

US Census Demographic Data + ZCTAs == AWESOME

ZCTAs are polygons fixed to match the census data. By using ZCTAs you get a consistent and accurate representation of a geographic area.

More info about ZCTAs from

4 replies on “Of ZIP Codes and ZCTAs”

  1. Great summary of zip codes.

    NOW… I tried American Fact Finder and I cannot locate 5 ACS 2010 poverty data to the ZTCA level….

    2000 Census data is there but NOT 5 year ACS.

    Any idea from Census as to WHETHER and WHEN they WILL publish poverty data to the ZTCA level in American Fact Finder or is downloadable somehow by FTP?

    Tom Cusack
    Oregon Housing Blog

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