Some economists put the productivity cost of housing difficulties at 1.6 trillion a year in the USA, which sounds about right: https://www.bloomberg.com/news/articles/2015-05-18/the-urban-housing-crunch-costs-the-u-s-economy-about-1-6-trillion-a-year. Also, I'd be interested to know how NZ's diaspora, mostly in favour of Australia, compares to that of an Australian state vis-a-vis the rest of Australia. From what I can see there's some population churn between states as you'd expect, and a steady net loss from other states to Queensland (a favoured retirement destination, the local equivalent of Florida), but NZ's haemorrhage is much more serious and chronic than any Australian state of comparable population. There are hundreds of thousands of Kiwis in Australia but stuff-all Australians in NZ, put it like that.