Centroid Matching
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. All six houses would have the same ZIP Code geocode because they all reside in the same ZIP Code. The four houses located in the dashed area of the diagram would have the same ZIP + 4 centroid returned, whereas the two houses that are outside of the dashed area would not since they don't reside in the ZIP + 4 Code area.