In reply to Matthew Carberry 382, "CDC's only prevented from spending money on studies designed to promote gun control":  

You are technically correct; that is the language in the 1996 rider.  And I'd approve that, if politics worked that way.   However, the CDC realized that some people would cry "advocacy" about any research result that society may be hurt by gun violence-- no matter if the studies were designed to avoid bias.  So they stopped doing the research. 

U.S. researchers (outside the CDC) now go to British databases for data on the US.