DEFINITION of 'Social Security Number - SSN'
A nine-digit number assigned to citizens, some temporary residents and permanent residents in order to track their income and determine benefit entitlements. The Social Security number was created in 1936 and while the original intention was just to track earnings and benefits, it is now also used to identify individuals and sometimes track their credit record.
BREAKING DOWN 'Social Security Number - SSN'
Social Security numbers are now random streams of digits, but prior to 2011, they were not. At that time, the first three digits represented the area in which the individual was born or was from. The next pair of numbers was originally slated to represent a year or month of birth. Because they worried about this being falsified, the Social Security Administration instead voted to have it represent a group number. The final four digits have aways been randomly generated.