The problem with your analysis is that it's not random. Higher IQ parents will tend to cluster and bring their kids with them. Even brilliant ne'er-do-wells like myself who'd otherwise be living hand to mouth are pulled into the cluster by our spouse choice.
I disagree with this - We are in a recognised non cluster - particularly now that we lost a good portion of our population and had it replaced with construction workers (not commenting on their intelligence level - just lost lots of teachers and professionals. We live here because of my partners work - which is not related in any way to his talents (or I would strongly argue his intelligence.)
In our city I guess there are smallish clusters, but we are not in one, and I think the bigger clusters are in the north island. South Island tends to attract doers not thinkers.... (massive generalisation sorry!)
