Comparing the GNP per capita of New Zealand to Australia gives some interesting results: https://www.wolframalpha.com/input/?i=%28gross+national+prod... The variance of the past few years (between 1:1 to 1:2) is quite high. I guess theoretically the biggest difference between the two countries is the mineral wealth of Australia?
Australia is doing unusually well recently, I think due to natural resources as you mentioned. This graph might give a better idea of what has been going on: https://www.wolframalpha.com/input/?i=uk+gdp+per+capita+%2F+...
Unfortunately for us, we pissed all that windfall up against a wall. I don't think we posted a current account surplus at all throughout the resources boom years. Instead, Australian banks borrowed money from overseas to lend to Australians so they could sell houses to each other for ever increasing amounts every year. The Australian economy grew because we borrowed from overseas. Existing property owners got to feel richer. As soon as we start to pay back all the debt in a significant way, our economy will shrink. Just as the dependent to worker ratio has peaked. We will have nothing to show for it. Certainly not fast internets.