California Outline


Are the data on this website for zips or ZCTAs?

Since the demographic data on this website 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. Examples of weird zip codes that we've run into in the past include a zip only for the IRS, a zip that is a single office building or a zip code with 0 or a small population. And sometimes there aren't enough samples in a zip/ZCTA to produce an estimate (i.e. small population).

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. In 8 years of selling this data to thousands of clients, we've run into 1 case where ZCTAs wouldn't work for a client's project. If you are doing a mass mail project, you may need zip code data instead of ZCTA data.

If you must have United States Postal Service ZIP Code service areas and not ZCTAs, we can either:

1. buy zip data on your behalf if the demographics you need are available from one of the private vendors that we work with or

2. we can license zip shape data from a private company and use these shapes to create custom demographic estimates. To get a quote from private data vendors, we need to know how many people will be accessing the data (number of users) and how you'll be using the data (i.e. internal analysis versus external facing app). Both of these options cost more than using US Census Bureau ZCTA data.

Full Citations for the data on

  • United States Census Bureau. "B01001 Sex by Age." 2011 - 2015 American Community Survey. U.S. Census Bureau's American Community Survey Office. Web. 8 December 2016 />
  • United States Census Bureau / American FactFinder. "Annual Estimates of the Resident Population: April 1, 2010 to July 1, 2016". 2016 Population Estimates Program. Web. March 2017. />
  • United States Census Bureau / American FactFinder. "DP03: SELECTED ECONOMIC CHARACTERISTICS". 2011 - 2015 American Community Survey. U.S. Census Bureau's American Community Survey Office. Web. 8 December 2016 />
  • United States Census Bureau / American FactFinder. "DP05: ACS DEMOGRAPHIC AND HOUSING ESTIMATES". 2011 - 2015 American Community Survey. U.S. Census Bureau's American Community Survey Office. Web. 8 December 2016 />
  • United States Census Bureau. 2000 Census. U.S. Census Bureau, 2011. Web. 17 October 2012 ftp:/>
  • United States Census Bureau. 2010 Census. U.S. Census Bureau, 2012. Web. 17 October 2012 ftp:/>

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