Social Security numbers are unique identifiers issued to each person by the Social Security Administration (SSA). The chances of two people having the exact same Social Security number are extremely small, but not technically impossible.
What is a Social Security Number?
A Social Security number is a 9-digit number in the format XXX-XX-XXXX. The first three digits are called the area number and represent the state where the Social Security card was issued. The next two digits are the group number and the last four digits are the serial number.
This structure allows for over 1 billion unique combinations. However, certain numbers are restricted from being issued. For example, numbers starting with 666 or 000 through 099 will not be used.
Are Social Security Numbers Unique?
When the Social Security program began in 1936, it was never intended to be a national identification number. It was simply meant as a way to track earnings and eligibility for Social Security benefits. At the time, it was believed the chances of duplicate numbers being issued was low.
However, as the use of SSNs expanded over the decades, the SSA began taking steps to increase uniqueness and prevent duplication:
- In 1973, the SSA began requiring proof of age and citizenship for children under 18 applying for numbers.
- In 2011, randomness was added to the assignment process as a fraud prevention measure.
- In 2022, the SSA began removing certain reusable prefixes from circulation.
The SSA claims numbers are now assigned through a robust process that generates unique combinations. As additional safeguards are added, the chances of issuing a duplicate grow increasingly unlikely.
Why Duplicate SSNs Were Issued in the Past
In rare cases, the same Social Security number has been issued to different people in the past. This occurred for a few key reasons:
- Data entry errors – Typos when inputting applications could result in a repeat number being generated.
- Fraud – Criminals using false identities could be issued a number already given to someone else.
- Early lax controls – Before digitization, minimal vetting meant numbers could be reused by mistake.
Experts estimate about 40 million Social Security numbers have been duplicated since the program’s inception. However, the vast majority occurred decades ago when controls were weaker. Instances today are very uncommon.
Are Duplicate SSNs Still Possible?
While exceedingly unlikely, there is still a mathematical possibility that two people could be issued the same Social Security number.
With about 900 possible 3-digit area numbers, 100 possible 2-digit group numbers, and 10,000 4-digit serial numbers, there are about 900 billion total combinations. However, exclusions remove many from possibility.
As of 2022, about 500 million Social Security numbers have been issued. With billions of combinations remaining, the chances of selecting the same number twice is infinitesimally small.
However, Social Security numbers are not generated in a truly random way. Area numbers are assigned by geographical region and group numbers are issued in a standardized order. So in theory, a duplicate is possible if:
- Two people applied from the same region on the same day
- They were given consecutive group numbers
- And were assigned the same random serial number
While the planets would need to align perfectly, a duplicate SSN could slip through the cracks. But with current safeguards, the odds of this happening are less than 1 in 1 billion.
Are Duplicate SSNs Checked For?
The SSA utilizes several verification methods to prevent duplicate SSNs from being issued:
- Numident database – A master file of all SSNs ever issued, used to check for pre-existing numbers.
- Social Security Number Verification System (SSNVS) – Allows private companies to instantly validate SSN/name combinations against SSA records.
- EV-STAR – An electronic verification system that quickly detects invalid or duplicate SSNs.
These systems check applications in real-time against the SSA’s master database. Potential duplicates are flagged for further investigation before issuance.
| Verification System | Year Introduced |
|---|---|
| Numident | 1936 |
| SSNVS | 2005 |
| EV-STAR | 2008 |
Additionally, the SSA runs regular internal audits to identify any duplicate numbers that may have slipped through. These redundant controls ensure near perfect uniqueness of all numbers issued.
What Happens if a Duplicate is Issued?
If the SSA determines a duplicate SSN was issued, they will rectify the situation right away by voiding the more recently issued number and issuing a new unique SSN to that individual.
When a duplicate surfaces, the SSA follows this process:
- Investigate how the duplication occurred and add safeguards to prevent reoccurrence.
- Void the SSN that was most recently issued.
- Notify the second individual assigned the number.
- Issue them a new SSN that has never been used.
- Update government records to replace the duplicate with the new SSN.
This ensures the integrity of the Social Security numbering system is maintained. Any hardships or inconveniences faced by someone re-issued a number are outweighed by the need to guarantee uniqueness.
Preventing Identity Theft
While duplicate SSNs today are extremely rare, identity theft involving Social Security numbers remains common. Since SSNs are valuable for committing financial crimes, thieves frequently target them.
The FTC estimates that 14.4 million Americans were victims of identity theft in 2018 alone. Many cases involved misuse of existing SSNs rather than obtaining duplicate numbers fraudulently.
| Year | Americans Affected by Identity Theft (Millions) |
|---|---|
| 2015 | 13.1 |
| 2016 | 15.4 |
| 2017 | 16.7 |
| 2018 | 14.4 |
To prevent identity theft, it is crucial to guard your Social Security number carefully. Some tips include:
- Do not carry your SS card in your wallet. Leave it in a secure place.
- Shred documents before throwing away.
- Do not give out your SSN unless absolutely required.
- Protect your SSN online by using strong passwords.
- Use multi-factor authentication when available.
- Monitor your credit reports regularly for suspicious activity.
Conclusion
In summary, the chances of two people having the exact same Social Security number are extremely remote. The SSA takes rigorous measures to ensure the uniqueness of each SSN issued. Duplicates are incredibly rare and swiftly corrected if discovered.
While an anomaly is mathematically possible, the odds of it occurring are less than 1 in 1 billion. For all practical purposes, every Social Security number ever issued has been unique and will likely remain so. Proper identity theft prevention measures are necessary, but concerns over duplicate SSNs in particular are largely unfounded.