THere is a culture in New Zealand of after leaving University going overseas to "See the world" (their OE: Overseas Experience). Many highly educated people end up staying there because of the more interesting/higher paying jobs.

However, after they start a family, it's fairly common for people to want to move back to New Zealand as it's seen as a great place to raise children. When people come back, they've acquired a large amount of experience from other places.