The population reached an estimated 4,331,600 at September 30, according to Statistics New Zealand.

The figure is up 1.2 per cent on the previous year - the highest growth in three years.

The median age for females is 37.5 years and men 35.5 - increases of 2.6 years for females and 2.2 years over 10 years ago.

The largest age group - 34 per cent - is 15-39, while 13 per cent are 65 and over.