Although the population is growing at its fastest rate in over a decade, people in New Zealand are still outnumbered by sheep.

New Zealand's population is growing at its fastest rate in over a decade, outpacing Australia's growth rate.

Estimates released by Statistics New Zealand today showed the country's population grew by 86,900 people, or 1.9 per cent, in the year to June 30 2015.

That figure was the result of net migration of 58,300 and natural increase of 28,700.

Statistics New Zealand senior demographer Kim Dunstan said net migration resulted from both high levels of arrivals and low levels of departures.

The biggest source for migrants remained the United Kingdom, followed by China and India, Dunstan said.

Kiwis who were returning after more than 12 months overseas were also counted as migrants.

Natural increase referred to the number of births minus deaths.

Statistics manager Vina Cullum said the last time the country's population grew at this rate was in 2003 when the increase was 2 per cent, and it last exceeded Australia's growth rate in 2004.

The working-age population is now equally split between younger (15-39) and older (40-64) people.

The two groups make up 33.3 per cent and 32.2 per cent of the total population, respectively.

Two decades ago, those aged 15-39 made up 38.7 per cent of the population while those aged 40-64 comprised just 26.7 per cent.

The total estimated resident population sits at 4,596,700.

People in New Zealand are still greatly outnumbered by sheep, which at June 30 2014 numbered 29.8 million.