WELLINGTON, Feb. 7 (Xinhua) -- New Zealand's estimated resident population could reach 5 million late in 2019 or in 2020 based on recent trends, after hitting 4.9 million at the end of September 2018, the country's statistics department Stats NZ said on Thursday.

It took 30 years to move from 3 million in 1973 to 4 million in 2003, but it is likely to take only about half that time to increase by another 1 million, about 16 years. In 1908, the country had just 1 million people living here, according to Stats NZ.

New Zealand's population is currently increasing by one person every 5 minutes and 26 seconds, according to Stats NZ's population clock.

Population growth reflects both patterns of migration and "natural increase," or the difference between births and deaths.

In the year which ended September 2018, the population increased nearly 90,000, Stats NZ said, adding more than two-thirds of that was from net migration, with the rest from natural increase, with 27,000 more births than deaths.

The 1.9-percent growth for the September 2018 year was slightly less than the high of 2.1 percent in 2016, it said, adding the much slower growth rate of 0.5 percent in 2012 was driven by natural increase, during a period when more people left New Zealand as migrants, than coming to stay.

For the past five years, net migration has been the dominant factor driving population growth, the department said, adding more than 1 million people born overseas now live in New Zealand, while hundreds of thousands of New Zealand-born live overseas, especially in Australia.

The latest 2016-base projections indicate that New Zealand will probably reach the 6-million mark in the mid-2040s. However, it could be as soon as the 2030s, particularly if migration remains at historically high levels.