I've got no link to back this up but I really think this article is misleading. I'm taking "incidents" to be a combination of arrests, seizures, and lab accidents? That number reflects a more aggressive stance by law enforcement in those states, but it sort of reads as if its nearly half of meth production. Which I'll dismiss as absurd with no link to back it up.
The Combat Meth Act of 2005 requires cold and allergy pills containing pseudoephedrine to be sold from behind the counter. Pseudoephedrine purchases are tracked and buyers must show identification. The amount that can be purchased is limited.
The internet was really the catalyst for the meth growth in the '90s. The mail order chemicals and fast adapting online recipes had every idiot in the rural South and his brother in the game.
Ten years ago meth was on the entire South like a plague from the Old Testament and the Suda-Fed restrictions largely shut it down. It wasn't entirely gone but there weren't thousands upon thousands of cookers cooking. But just in the past 1 to 1-1/2 years, its back. Maybe not to the 2000 levels but closing in.
Oh, and POSSUM