I doubt you'll find a definitive answer for this, but here are a couple of places where you can try to look for information:
http://www.fedstats.gov
http://www.ask.com
Type your QUESTION in the search box. You'll probably get a screen or two that ask you to clarify or narrow the focus of your question.
how many children(aged under 18) are taking drugs?
2 answers
thank you very much , though what it fedstats? how do you use it?