The country's population is projected to hit 6 million at the end of the century according to a United Nations report.
The 2017 Revision of World Population Prospects puts New Zealand's population at 4.7 million, and growing to 6.1 million in the year 2100.
The report put New Zealanders life expectancy at 82 years, which will be the global average in 2100. New Zealanders are expected to live to 92 by the end of the century.
While New Zealand's population is on an upwards trend, China - the most populous country with 1.4 billion people - is predicted to peak in the year 2030 and then decline and fall into second place.
India, with the second largest population, will fluctuate but be the largest in 2100 with an expected population of 1.5 billion people.
The report estimated the world's population would grow by about 83 million people each year, with rapid population growth in Africa.
"Between 2017 and 2050, the populations of 26 African countries are projected to reach at least double their current size. For six African countries, the populations are projected to increase by 2100 to more than five times their current size: Angola, Burundi, Niger, Somalia, the United Republic of Tanzania and Zambia," the report said.
Africa's population would more than triple from now to 2100 to reach 4.4 billion, or 40 percent of the world's population.
"The large numbers of children and youth in Africa today will reach adulthood in future decades. Because of their large numbers, their childbearing will contribute to a further increase of population even assuming that they will bear fewer children on averatge than their parents' generation."