Now do this for the whole world, and multiply these stats by the arability of the land and the necessity of climactic intermediation (i.e. thick clothes/central heating/air conditioning) and you get a map of "where everyone would immediately get up and move to, if they were rational agents and there were no political considerations."

Aside: I've had a hypothesis for quite a while that the land most fought-over in land wars (or holy wars) has extremely low value on such a map. I'd love to see the data to confirm/refute that.