FAQs

Why Is Zip Code X Missing? Or what is a ZCTA, and how is it different from a zip code?

Since the demographic data on this website and in the reports is from the US Census Bureau, we’re using the US Census Bureau’s ZIP Code Tabulation Areas (ZCTAs), which are generalized areal representations of United States Postal Service ZIP Code service areas.

A zip code is technically a linear postal route. I like to imagine zips codes as a postman driving in a line up and down streets delivering mail. Here’s a fun animation about how the Census Bureau turns linear routes into polygons:

Sometimes, there isn’t a ZCTA for a "weird" zip code. The most common example of "weird" zips are PO Box zips (so zips of only businesses and no residents, and you need residents for demographic estimates). Other weird zips that we’ve run into in the past include a zip only for the IRS or a post office. And sometimes there aren't enough samples in a zip/ZCTA to produce an estimate (aka too few people living in the zip).

On this website, we use the terms ZCTA, zip code or zip interchangeably, because most people who we work with don’t know what a ZCTA is and the difference between a zip code and ZCTA doesn’t impact how they need to use the data. But theoretical problems could arise with using ZCTAs if you are doing a mailing list or mass mail project.

What to do if you HAVE to have demographics for a zip that doesn't have a ZCTA?

Check out this handy zip to ZCTA crosswalk.

How Could You Use This Crosswalk?

Let’s say you were asked to rank a list of addresses from most likely to buy to least likely to buy. Since this is a quick test to see if using demographic data will improve your close rate, you are going to simply associate each lead with some basic demographics for the zip like median household income. 90% of your addresses have zips that match ZCTAs, so it’s easy to match these leads with their ZCTA demographics. But the remaining 10% of your addresses don’t have a matching ZCTA. You could then use the above crosswalk to associate the “weird” zips with a ZCTA and thus pull demographics for the rest of your addresses.

Got more zip/ZCTA questions? Contact us.

Full Citations for the data on wisconsin-demographics.com

• 2018 TIGER/Line Shapefiles (machine readable data files) / prepared by the U.S. Census Bureau.
• United States Census Bureau. Annual Estimates of the Resident Population: April 1, 2010 to July 1, 2019. U.S. Census Bureau, Population Division. Web. May 2020. http://www.census.gov/.
• United States Census Bureau. B01001 SEX BY AGE, 2018 American Community Survey 5-Year Estimates. U.S. Census Bureau, American Community Survey Office. Web. 19 December 2019. http://www.census.gov/.
• United States Census Bureau. DP02 SELECTED SOCIAL CHARACTERISTICS IN THE UNITED STATES, 2018 American Community Survey 5-Year Estimates. U.S. Census Bureau, American Community Survey Office. Web. 19 December 2019. http://www.census.gov/.
• United States Census Bureau. DP03 SELECTED ECONOMIC CHARACTERISTICS, 2018 American Community Survey 5-Year Estimates. U.S. Census Bureau, American Community Survey Office. Web. 19 December 2019. http://www.census.gov/.
• United States Census Bureau. DP04 SELECTED HOUSING CHARACTERISTICS, 2018 American Community Survey 5-Year Estimates. U.S. Census Bureau, American Community Survey Office. Web. 19 December 2019. http://www.census.gov/.
• United States Census Bureau. DP05 ACS DEMOGRAPHIC AND HOUSING ESTIMATES, 2018 American Community Survey 5-Year Estimates. U.S. Census Bureau, American Community Survey Office. Web. 19 December 2019. http://www.census.gov/.