Breaking: US midwest to launch regional cap-and-trade scheme

According to Point Carbon, Wisconsin governor Jim Doyle announced today that the midwestern states will join together in a regional cap-and-trade scheme to reduce greenhouse gas emissions.

This hasn’t hit any media outlets yet, so that’s all I’ve got. If true, what percentage of the U.S. is now operating under some sort of mandatory carbon cap? All of the west is linking up, the northeast has banded together, and now the midwest. If counted by population or, more importantly, GDP, that’s got to be a large majority of the U.S., right?