Rat Capital?

I saw an article (and heard on the news) that Chicago is now the nation's rat capital. How is this possible? Does Chicago have more of a rat problem than New York? Not bloody likely. Now there are a lot of things to criticize Chicago for: an awful mayor, high crime, ridiculous taxes, etc., but I find it hard to believe that the Windy City has more rats than New York. Every time I'm in New York and ride the subway (which I do pretty much every time I'm there for a visit), I see rats on the tracks. Granted, Chicago's L system is largely elevated, so I doubt rats are climbing the rails in the city and I only recently started working downtown in the city, so maybe the rats are there and I just haven't seen them in full force yet. Still, given the populations and the housing in New York versus Chicago, I still believe the Big Apple is chock-full of rodents. I read a book years ago called Rats and it was about the rat epidemic in New York and I also recently saw a documentary about rats in New York and both the book and the documentary were fascinating. You learn the habits of the rats and come to understand why they do what they do. In the book, the author wrote about an Irish pub somewhere in New York and how the rats seemed to know when it was pot pie night because they showed up in droves to get to the garbage the put out that night. Gross.