Osteopathic physicians make up about 6% of the total physicians today. The data I have on number of DO's in each specialty is from the 1999 AOA databook. In 1999 Osteopathic physicians made up about 4.5% of total physicians.
As far as pediatrics - in 1999, about 2% of DO's were pediatricians. So they were underrepresented. The fields in which DO's were overrepresented in 1999 were EM (12%) and FP (27%). All other specialties ranged from 1-4%.
Interestingly, when you compare the % of physicians in a specialty that are osteopathic to the % of total physicians in that specialty, it is IM and Peds where DO's are the most underrepresented. (18% of total physicians were IM, only 2% of DO's. 7% of total physicians were Pediatricians, only 2% of DO's.) There are as many DO's in orthopoedic surgery, general surgery, radiology, and anesthesiology as there are in pediatrics!
Just some interesting data I thought.