The California Public Employees' Retirement System, the largest U.S. public pension program, said Wednesday it accidentally printed the Social Security numbers of almost half a million retirees on brochures mailed last week.
A mail-processing computer inadvertently added recipients' partial or full Social Security numbers to mailing labels attached to brochures sent to 445,000 retirees announcing a board election, CalPERS spokesman Brad Pacheco said.
The fund sent letters to its members apologizing and promising new procedures to prevent future mix-ups.
Social Security numbers are often used by identity thieves to fraudulently open or access credit card accounts and steal money and products.
An April 2007 report by the federal Identity Theft Task Force identified the Social Security number as "the most valuable commodity for an identity thief."