Deconstructing the SSN
As a result of the June 1936 decision, the current SSN is composed of three parts:
The first three digits are the area number
The next two digits are the group number
The final four digits are the serial number
The 3-digit area number is assigned by geographic region. In 1936 the Social Security Board planned eventually to use area numbers to redistribute work to its 12 regional centers to serve workers in those areas. One or more area numbers were allocated to each state based on the anticipated number of SSN issuances in the state.3 Prior to 1972, the numbers were issued to local offices for assignment to individuals; it was thought this would capture information about the worker's residence. So, until 1972, the area number represented the state in which the card was issued. (Barron and Bamberger 1982, 29).
Generally, area numbers were assigned in ascending order beginning in the northeast and then moving westward. For the most part, people on the east coast have the lowest area numbers and those on the west coast have the highest area numbers. However, area numbers did not always reflect the worker's residence. During the initial registration in 1936 and 1937, businesses with branches throughout the country had employees return their SS-5 Application for Account Number to their national headquarters, so these SSNs carried the area number where the headquarters were located. As a result, the area numbers assigned to big cities, such as New York, Philadelphia, Boston, and Chicago, were used for workers in many other parts of the country (McKinley and Frase 1970, 373). Also, a worker could apply in person for a card in any Social Security office, and the area number would reflect that office's location, regardless of the worker's residence.
Since 1972, when SSA began assigning SSNs and issuing cards centrally from Baltimore, MD, the area number has been assigned based on the ZIP code of the mailing address provided on the application for the original Social Security card. The applicant's mailing address may not be the same as the place of residence.
Some exceptions to the general east-to-west, ascending-order area numbering scheme exist:
Sequence 700 through 728 was assigned to railroad workers until July 1963.
586 was divided among American Samoa, Guam, the Philippines, Americans employed abroad by American employers and, from 1975 to 1979, Indochinese refugees.
580 was assigned to Puerto Rico and the U.S. Virgin Islands; sequences 581 through 584 and 596 through 599 were also assigned to Puerto Rico.
Sequence 577 through 579 was assigned to the District of Columbia.
Sequences 587 through 588 and 589 through 595 were assigned to Mississippi and Florida, respectively, for use after those states exhausted their initial area number allotments.
Sequence 729 through 733 has been allocated to the Department of Homeland Security (DHS) for SSNs issued through the Enumeration at Entry (EaE) program, described below.
No SSNs with an area number in the 800s or 900s, or with a 000 area number, have been assigned.
No SSNs with an area number of 666 have been or will be assigned.
SSA has many years' worth of potential SSNs available for future assignment. However, because of population shifts, SSA now faces an imbalance in the geographic allocation of area numbers. Some states have a current allocation of SSNs that will last for many years, while others have a pending shortage. As a result, given present rates of assignment and existing geographic allocations, several states currently have fewer than 10 years' worth of SSNs available for assignment.
In a July 3, 2007, Federal Register notice, SSA solicited public comment on a proposal to change the way SSNs are assigned (SSA 2007b). Under this proposal, SSA would randomly assign SSNs from the remaining pool of available numbers, and the first three digits would no longer have any geographic significance. SSA contends that doing so would ensure a reliable supply of SSNs for years to come, and would also reduce opportunities for identity theft and SSN fraud and misuse. SSA plans additional discussion with other government entities and the private sector before implementing any change.
The group number (the fourth and fifth digits of the SSN) was initially determined by the procedure of issuing numbers in groups of 10,000 to post offices for assignment on behalf of the Social Security Board's Bureau of Old-Age Benefits. The group numbers range from 01 to 99 (00 is not used), but for administrative reasons, they are not assigned consecutively. Within each area number allocated to a state, the sequence of group number assignments begins with the odd-numbered group numbers from 01 to 09, followed by even group numbers 10 through 98, then even numbers 02 through 08, and finally odd numbers 11 through 99.4
The last four digits of the SSN are the serial number. The serial number represents a straight numerical series of numbers from 0001–9999 within each group. Serial number 0000 is not assigned.