As noted earlier, everyone from President Obama to the Mexican ambassador is claiming that 90%, or even 95% of criminal guns recovered in Mexico come from the US. The fact that 90% of guns submitted to ATF for tracing trace to the US, but the Mexican government only submits guns that it thinks came from the US; a while back FoxNews ran the numbers and concluded that only 17% of guns recovered in Mexico came from the US. Now Factcheck.org reruns the numbers and concludes it's more like 34%, still a minority.

One mystery remains: the difference between the two sets of numbers is explained as the smaller one reflect guns that could be traced to a particular State, the larger one includes those that couldn't be. A successful ATF trace at the very minimum tracks it to retail dealer, thus you know the State. If they couldn't report the State, it probably means an unsuccessful trace -- we know that Colt made it in the US, but can't trace it to the dealer. Unsuccessful traces are disproportionately traces of sales long ago -- those made before the 1968 GCA are about hopeless, and even subsequent to that, the farther back in time, the more likely records have been misplaced.

Which would suggest, at least, that about half of the traces relate to very old gun transfers. Say a gun was sold at retail in 1960, has gone thru 2-3 legit owners since then, a burglar steals it and fences it across the border -- that'd go down as a gun "traced to an American source," and be portrayed as if it was a straw man sale or crooked dealer.

The other possibility is that guns not traced to sale in a particular State include guns not sold in the US at all, but exported. In 2007, American manufacturers exported 10,530 handguns and rifles to the Mexican Ministry of Defense. Think the cartels have enough money to get their hands on as many as they want?