Love 'em or hate 'em (no really, love 'em), they'll be here as long as we are.
Rats are political. Yes, I know all the jokes. But what I really mean is that the decisions about where there will be rats and where there won't be are all snarled up in politics.
For a great local example, consider the 2004 article in Pest Management Professional. Headline - "Adriaen's Landing, A Rodent IPM Success Story" (you can find it in the links to the right of this note). I'll boil it down for you: They were gonna develop those 30 acres, they had more than the usual amount of rat control money available (I'm not sure why that was, but cronyism drove a lot of decisions on that project).
Driving all the indigenous rats from the site into downtown was going to cause all kinds of trouble, so they used the latest technology. They were probably helped by the fact that all the restaurants that were supposed to spring up there never got built, and as of this writing, the biggest problem was the occasional rat wandering over from one of the poorer neighborhoods. That rat was immediately killed. It's all about resources.
***This episode originally aired on March 12, 2012***