ZIP Code centroid matching is a center point of an area defined by either a ZIP Code or a ZIP+4, and is the least accurate type of geocode. A ZIP centroid is the center of a ZIP Code; a ZIP+4 centroid is the center of a ZIP+4. Since a ZIP+4 represents a smaller area than a ZIP Code, a ZIP+4 centroid is more accurate than a ZIP Code centroid.
The following diagram illustrates centroid matching. In the following example:
Only four of the six houses would have the same geocode in this example because only the four reside in the same ZIP+4 code.
