, that article doesn't say that about 300,000 live there undocumented. From the article........
"Okay, fine. But... what happened to the "other" 300,000 or so Americans cited by less official sources?
The Embassy staff who assisted me in this verification commented that, "The number strikes us as low . . . There are certainly MANY Americans who cross into Mexico via land border who never register with immigration. We at the consular services see a great number of Americans who have been here as long as a year without so much as a passport." They were quick to add, "In any case, the Mexican authorities are the official source for such data
Also from your article....."However, I find it difficult to believe that more than an additional 15,000 to 20,000 persons make up these FMT holders and "slipped through" categories; certainly, 375,000 people have not slipped through.
Regardless, this was published back in 2000, and it is an article by one person who did this as a project, and he was given very limited information.