>I want to live in a liberal democracy with a high standard of living and low carbon emissions (so apartments close to amenities with lots of bike lanes and very few automobiles) with a steady or slowly decreasing population, because there are too many people in the world for it to support. If such a place existed (Denmark comes to mind, or perhaps Japan), it would probably be a desirable target for migrants from all over the world, which would strain the systems that could make such a place possible.

Yes, but I think that's what happens at t=0. And I think that your preferences are probably widely shared by a large contingent of the world population. As it stands, those who enjoy it are either those who had the good fortune to be born in those societies, or those who manage to migrate there through some way or another. Yes, perhaps immigration initially makes it less feasible for those societies to continue operating like that, but it makes it MUCH more difficult to governments who don't support those policies from existing. That's the factor that I put a lot of faith in. The important factor in my eyes is not just the influx of immigrants, but the exodus which will force other countries and governments too look much more like the Danish one (in your example) if they are to survive.

Google and Facebook fight over employees, and the ultimate winners are engineers in place to be hired by those companies. Elsewhere in our economy and the world, we seem to understand that in competitive environments, "customers" win.

Within the US we understand that too! Just take all the states who try to entice businesses through tax policy, old people who move to warmer climates, etc. You don't hear nearly as much complaining about state and local politics (which accounts for a much larger swath of gov't spending than national politics) here in the U.S. And I think some of the issues you mention ARE present. There are municipalities and states that offer friendlier policies in one shape or another, and you do see athletes moving to Florida because of the lack of income tax, for instance. But I think those issues are far, far outweighed by what the country gains by having these "open borders" between the states.

I suspect we don't have more issues because if you don't like something about where you live, you move. This is one of the most distinct things about the U.S. with my experience overseas (I'm from Brazil originally).

For better or worse, accessing a modern economy there means living in one of two cities. Here? I can make a rich matrix of climate, culture, job environment, etc., and find a few candidate cities in which to live in. That's amazing. And I think that's how you get some pretty unique experiences -- Silicon Valley to NYC -- which are all world-class.

With respect to your housing point, I think you are right. But again, I see greater migration as a way to also solve those problems. The influx makes land and housing more valuable in Denmark, which in turns makes more development there more valuable and more feasible. And, conversely, makes places people are leaving less valuable and land there cheaper.

I see it as a way to equate opportunity over the world. And, like in the U.S., no doubt that the steady state will yield places that are very different from one another in terms of culture, or climate, or how it is run by their local government. But the threat of exit will be a great check on their ability to diverge from the will of and preferences of the people.