Social security numbers can and have been issued to multiple people[1]. And some people have been issued multiple social security numbers[2] (which would allow

Social security numbers can and have been issued to multiple people[1]. And some people have been issued multiple social security numbers[2] (which would allow them to vote more than once). Social security numbers are not a good unique identifier. [1] http://www.pcworld.com/article/3004654/government/a-tale-of-two-women-same-birthday-same-social-security-number-same-big-data-mess.html http://www.pcworld.com/article/3004654/government/a-tale-of-... [2] http://oig.ssa.gov/audits-and-investigations/audit-reports/A-02-14-34054 http://oig.ssa.gov/audits-and-investigations/audit-reports/A...