Sort of a meta-comment, but that is a very very nice graphic.
Also, the job growth numbers for each city look suspicious. Was there such a jump in growth rate in Jan '11?
Can't speak to the job growth numbers methodology as they come from SimplyHired.com
If you have more specific JS questions than that I can point you at @golike who wrote all the code for this :)
Sorry, that wasn't supposed to be a joke. A meta-comment is a comment about comments, though, and your comment is on the graphics.