GDP isn't the economy. The economy can grow to some limit but will stop, and it will be more expensive, in terms of things we don't currently assign value to like water, air, quiet, peace in order to get there.<p>Another question is "what's it worth?" since the rat race will continue for quite a while. Some people think it's important that the earth hold 30 billion people, as if they wanted to live shoulder to shoulder and eat factory food.