TABLE 1.

—Technical Definitions of and Distinctions Between Zip Codes and Zip Code Tabulation Areas (ZCTAs)

Definition of ZCTAs11

“ZIP Code Tabulation Areas (ZCTAs™) are a new statistical entity developed by the US Census Bureau for tabulating summary statistics from Census 2000. This new entity was developed to overcome the difficulties in precisely defining the land area covered by each ZIP Code®. Defining the extent of an area is necessary to accurately tabulate census data for that area. ZCTAs are generalized area representations of US Postal Service (USPS) ZIP Code service areas. Simply put, each one is built by aggregating the Census 2000 blocks, whose addresses use a given ZIP Code, into a ZCTA which gets that ZIP Code assigned as its ZCTA code. They represent the majority USPS five-digit ZIP Code found in a given area. For those areas where it is difficult to determine the prevailing five-digit ZIP Code, the higher-level three-digit ZIP Code is used for the ZCTA code. Since we take the ZIP Code used by the majority of addresses in an area for the ZCTA code, some addresses will end up with a ZCTA code different from their ZIP Code. Also, some ZIP Codes represent very few addresses (sometimes only one) and therefore will not appear in the ZCTA universe.”

Distinction between ZCTAs and Zip Codes12

“Even though the codes may appear the same, the addresses and areas covered by these areas may not be the same. We strongly advise data users who wish to compare 1990 and 2000 data to determine and evaluate any coverage differences that exist before making any comparisons. There are several reasons for this caution: The USPS has extensively modified ZIP Codes over the last ten years. Even though a 1990 ZIP Code matches a Census 2000 ZCTA code, there is no guarantee that these cover the same geographic area. Also, some ZIP Codes in the 1990 data products were discontinued by the USPS, and new ZIP Codes were created; ZCTAs and the 1990 data products were discontinued by the USPS, and new ZIP Codes were created; ZCTAs and the 1990 census ZIP Code areas were delineated using different methodologies and therefore may not have comparable coverage area or size; and the Census 2000 ZCTAs will include some dedicated PO box ZIP Codes. All dedicated PO box ZIP Codes were excluded as ZIP Code areas in 1990. The resulting 1990 areas include data for both PO box ZIP Codes and the ZIP Codes that provide street or rural route delivery to the surrounding area.”