One expert is concerned about New Zealand's rapid population growth.
Statistics NZ has revealed that our resident population reached an estimated 5 million at the end of March.
It's the fastest million in our history, taking 17 years since reaching four million in 2003.
Massey University Sociology Professor Paul Spoonley says that growth has created challenges.
"If you think back over the 17 years, you would have heard about the traffic in Auckland, and the unavailability of housing. All the pressures that have been put on our infrastructure, and that's because we've been growing so fast."
He hopes hitting the milestone will let us focus on different issues.
"We're projecting that Auckland will close to be home to about 40 per cent of all New Zealanders. So is that something we actually want, or do we want to encourage population to go to our regions?"
However, the next milestone is not expected to come around as quickly.
Senior demographer Kim Dunstan says that hitting the 6 million mark might take a bit longer - sometime in the 2040s.