Definition: Established by the United States Postal Service, the use of five-digit Zoning Improvement Plan (ZIP) Codes everywhere in the United States was designed only to improve the speed of mail delivery. Every address was assigned a ZIP Code by the time the program began in 1963.
Also Known As: Zoning Improvement Plan Code
Common Misspellings: zip code (the lower case "zip" is not appropriate)
Examples:
ZIP Codes should not be used for mapping because they are neither political units nor are they equally sized in area, households, or population.
