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!)
The world "tend" does not imply a hard and fast rule. You don't happen to live in a cluster. Does that mean they don't exist, or don't happen very often? And no offence, I love NZ and kiwis, but it is such a tiny country (smaller than the metro area I live in, the whole population of the South Island is smaller than many cities, and they're certainly not within commuting distance of each other!), outliers are going to have few peers over the whole country, let alone in one very small town or city. But, I'll bet if you went to the suburb with single family homes closest to a large university you'd find the local school's IQ average was over 100, or the suburb where a hospital's staff tend to live, or some big engineering company.
