One of the advantages for employees in a group health plan is the contribution most employers make toward the cost of the health coverage premium â in many cases, employers pay one-half or more of the monthly premium for an employee.
The basic format consists of five decimal numerical digits. An extended ZIP+4 code, introduced in 1983, includes the five digits of the ZIP code, a hyphen, and four additional digits that determine a more specific location within a given ZIP code. The USPS provides a free online lookup tool for ZIP codes.
Within a given file, the records are sorted by 5-digit ZIP code. Each file is compressed as a zip archive (WinZip). This database also includes the US Postal Service city-state file, which contains a complete listing of the approximately 42,500 5-digit ZIP codes currently assigned by the USPS. This file has approximately 77,800 fixed-field-length ASCII records of 129 bytes each.