In addition to the ZIP Plus 4 Database Premium Plus Centroids file, this product also includes a file containing approximately 6 million ZIP+4 records that have coordinates representing either an interpolated Z4, a ZIP+2, or a 5-digit ZIP centroid. The positional accuracy results for these records did not have the geographic elements required to meet our quality criteria. However, these records are provided as they can still be used for more broad-based location matching and analysis.
The unmatched file has the same record layout as the Centroids file but does not contain Census tract, block group, or block values.