I don't think you quite understand the statistic, because the legal-versus-illegal, retail-versus-black-market issue doesn't affect the statistic at all. You don't need a gun's serial number or date of purchase in order to record a crime committed with a gun versus a crime stopped with a gun.
If police find a bullet-riddled body in a dumpster, a check mark goes in the "crime committed with a gun" column, even if the murderer or the gun is never identified. If an ex-husband shoots a bullet into his ex-wife's home, that's a crime committed with a gun, even when it's not found. When a masked man sticks a revolver in someone's face and takes their wallet, without firing the gun, that's a crime committed with a gun, even if the man or the gun is never found.
When a homeowner stops a home invader by holding him at gunpoint until police arrive, that's a crime stopped by a gun. When a woman presses a snub-nose revolver into the gut of an attempted rapist and pulls a trigger, that's a crime stopped by a gun.
The CDC has compiled statistics, and the latter category outnumbers the former category several times over.
And I thought about why Obama used the CDC instead of the FBI. FBI, as law enforcement, is populated by cops (who tend to be conservative and pro-firearm). The CDC, as a bunch of doctors, tends to be more politically liberal and thus more anti-firearm. Obama stacked the deck in an attempt to get as anti-firearms findings as possible, and despite that, the findings were very pro-firearm in terms of self-defense and crime prevention.
Obama is NOT a Republican puppet. He's the head of the Democratic Party and has beaten Republican candidates in elections twice. He pushed through a massive health care law that Republicans considered both unconstitutional and economic suicide. Puppets don't do that to their puppetmaster. Your comment betrays a misunderstanding of the American political system. I don't mean this as a personal attack--I know basically nothing of Dutch politics, so I'm not going to throw stones--but I would recommend you scrap that idea quick.