Document counterfeiters often choose a Social Security number at random when creating a fake card. That can mean trouble for somebody else.

Because about half of all available numbers already have been assigned to someone by the Social Security Administration, a person's identity is often compromised when the fake documents are used. In one study, the Social Security Administration found that 75% of Social Security numbers used for fraud had been assigned to someone else.

The Federal Trade Commission estimates that 17% of identity theft in California is committed for employment purposes. Four Central Valley cities -- Madera, Merced, Bakersfield and Visalia -- are among the top 11 cities nationally with the highest identity-theft rates. Fresno, Stockton and Modesto are in the top 40.

Victims learn all too late that they have inherited someone's arrest record, credit record, tax bills and medical history. They are turned away from jobs, denied loans and unemployment benefits, or even wrongly detained by police.

In an effort to avoid detection by E-Verify, an online government program that tries to detect fake documents, vendors increasingly use stolen identities -- including names, ages and Social Security numbers -- by digging through mail or scouring for information online.

Sometimes illegal immigrants bypass the fake-document vendors. They simply assume a friend's name and borrow documentation.

Jack Smith, a farmer in Livingston, said that before he took over a 1,700-acre sweet-potato farm last year and implemented strict hiring policies, some workers would apply for a job using one name but then use a different name after they start working -- a sign the worker likely assumed someone else's identity to get the job.

Or a worker who was not hired because he didn't have any papers would show up a few days later -- using a different name.

Said Smith: "All of a sudden he would have full documentation."

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