The answer is that he doesn't know, and can't know until there is a study that is designed to compile results that can be extrapolated to the general population. Power says he and others at Carnegie Mellon University are considering such a study, but none is planned yet.

Meanwhile, it doesn't make a lot of difference what percentage of children's IDs are stolen, Power says. If you're the one it happens to, it's a nightmare, and most people don't even consider it as a possibility. "The other dimension is to raise awareness of this as an issue," he says.

In some cases parents with bad credit ratings use their children's Social Security numbers to open accounts with utility companies so they can get water and electricity without intending to harm the children's credit, Holland says. In other cases, criminals use the number to profit. Some are used by people in the country illegally who are trying to establish credit, and buy houses and cars.

The database used for the study was all the people under 18 that were listed in All Clear ID's 800,000-plus database of people whose personally identifiable information had been compromised. The firm is hired by businesses that suffer data breaches and want to extend some protection to those who could become victims, says Bo Holland, All Clear ID's CEO.

In most cases, identities endangered by data breaches do not fall under systematic attack, Holland says. The identities are compromised, but don't appear to be taken by someone who then actively tries to capitalize on them. Names that fell under targeted attacks were dropped from the database used for the study, he says.