George - I looked at the GPI link you sent us. It is great that you got a population indicator in there. However, after leafing through the document I find it to be lacking in general. It seems the group has picked items and indicators that will be hard to measure and/or yield nebulous results at best. This will make it a hard sell to the perpetual growth advocates who love the GDP.
Maryland was the first state to adopt the GPI and their set seems to be a good balance of economic and social indicators. Add population/carrying capacity and I think you have a good model to work from.