William La Jeunesse and Maxim Lott of Fox News offer this (video report here):

You've heard this shocking "fact" before -- on TV and radio, in newspapers, on the Internet and from the highest politicians in the land: 90 percent of the weapons used to commit crimes in Mexico come from the United States...

...There's just one problem with the 90 percent "statistic" and it's a big one:

It's just not true.

In fact, it's not even close. The fact is, only 17 percent of guns found at Mexican crime scenes have been traced to the U.S.

What's true, an ATF spokeswoman told FOXNews.com, in a clarification of the statistic used by her own agency's assistant director, "is that over 90 percent of the traced firearms originate from the U.S."

Those listed as spreading the misleading figure include: Hillary Clinton, Bob Schieffer of CBS News, Dianne Feinstein, and William Hoover of the BATF.