http://www.connectforkids.org/node/223
(snip)
For instance, of those nearly 800,000 children reported missing each year, 99 percent are found through law enforcement efforts, according to FBI statistics. That still leaves 8,000 to 10,000 missing despite a prolonged search�a frightening, but certainly far more manageable, number.
We know that the vast majority of those missing have been taken by a non-custodial parent, have run away, or have been thrown out of their homes. The number of children kidnapped by others is far smaller, though absolutely devastating in every case.
About 200 to 300 children are kidnapped in the classic sense each year, according to the National Incidence Study of Missing, Exploited, Runaway and Throwaway Children (NISMART). Another 3,200 to 4,600 are taken for shorter periods, have something done to them, often a sexual assault of some type, and are then released. This number could be two to five times higher than the NISMART estimate, some believe, because of underreporting to law enforcement.