University of Illinois Urbana‑Champaign

Geographic Region: ZIP codes

A postal ZIP code is a delivery route and a Zip Code Tabulation Area (ZCTA) is a geographic area used by the U.S. Census Bureau. Postal ZIP codes change every year while ZCTAs change every 10 years.

The IECAM database provides data for both types of ZIP codes.

  • Postal ZIP code
    This is what people generally think of when they think of ZIP codes. There are many parts of the United States that do not have ZIP codes because they are not on postal delivery routes.
  • ZIP Code Tabulation Area (ZCTA)
    These are artificial areas created by the Census Bureau using census blocks. The ZCTA is roughly similar to the geographic area of a corresponding postal ZIP code (for those postal ZIP codes that approximate geographic areas).

These two ZIP code types are not precisely comparable. For example, a child care center with a postal ZIP code of 618xx may not be located in the ZCTA 618xx. Because postal ZIP codes change every year and that ZCTAs do not, there might be postal ZIP codes that have no corresponding ZCTA, and vice versa.

Data available on IECAM

IECAM presents data by postal ZIP codes for all years for the number and capacity of early care and education site-based services (PFA, Head Start, child care). These data are user-reported. IECAM has found many early care and education programs report (type in) the wrong postal ZIP codes for their sites. IECAM tries to correct obvious errors, but it cannot guarantee all postal ZIP codes are accurate.

Non-site-based service data (e.g., home visiting, early intervention) are not presented by postal ZIP codes or ZCTAs. Because the Census Bureau does not estimate data by postal ZIP codes (because they are not geographic areas), IECAM cannot provide demographic data by postal ZIP codes.

IECAM presents early care and education site-based data and demographic data by ZCTAs. A new set of ZCTA boundaries are released by the Census Bureau every 10 years. On the IECAM database, data for 2010 through 2020 are presented based on the 2010 ZCTAs. Data for 2021 and later are based on the 2020 ZCTAs. No data for 2009 or earlier are available by ZCTA. Source of definitions: U.S. Postal Service, ZIP Code – The Basics; U.S. Census Bureau, Geography Division. Geographic Terms and Concepts – ZIP Code Tabulation Areas