New Zealand's population grew by more than 100,000 in the year to June, the largest ever increase in a year.
The population is now estimated to be 4.79 million.
Net migration contributed 72,000 to the growth.
Over the past five years, New Zealand's population grew by nearly 400,000 - more than the population of Christchurch city.
Half of last year's growth was in the 15-39 age group.
But the numbers of older people were also spiralling upwards.
The number of people older than 90 is now 30,000, compared with 20,000 in 2007.