NHTSA Data on Bicyclist Deaths and Injuries in 2002 (last year analysed)
From Austin Bicycle Helmet Law
"In 2002, 662 bicyclists were killed, and approximately 48,000 were injured in traffic-related crashes. Children aged 14 and under accounted for 141 (21 percent) fatalities, making this one of the most frequent causes of injury-related death for young children.
(Source: http://www.nhtsa.gov)