Statistics released this morning showed there were 19,071 more births than deaths in 2023.
Stats NZ said this was the lowest annual natural increase since World War 2 - in 1943, there were just 17,562 more births than deaths.
In total, there were 56,955 live births and 37,884 deaths registered in New Zealand in 2023.
"The number of deaths in 2023 was slightly lower than in 2022, but higher than in the years prior," population insights analyst Rebekah Hennessey said.
Based on death rates during 2021-2023, a newborn boy could expect to live an average of 80.3 years, and a newborn girl 83.7 years.
These life expectancies are slightly higher than they were in 2017-2019 (80 and 83.5 years), and slightly lower than they were in 2020-2022 (80.5 and 84 years).
"The record number of deaths in 2022 - caused by the Covid-19 pandemic as well as population growth and ageing - has suppressed gains in life expectancy," Hennessey said.
In simple terms, the number of deaths generally increases as the population both grows and becomes older. The number of births, however, is driven by a more complex mix of social and demographic factors that change over time, Stats NZ said.
It said that live-birth figure was also relatively low.
"2023 had the lowest number of births registered in 20 years," Hennessey said.
That was despite a 3 percent increase in the number of women aged between 15 and 49 - when most births occur.
This combination - fewer births and more women of child-bearing age - resulted in a record-low fertility rate of 1.56 births per woman.
The total fertility rate has been below the replacement rate of 2.1 births per woman since 2013. The replacement rate is the number of births women need to have on average for the population to replace itself in the long term, with no migration.
The fertility rate refers to the average number of births that women in New Zealand would have over their lifetime, given current birth rates.
"The latest decline reflects a continued trend of smaller average family sizes and increased rates of childlessness, although the total fertility rate is also affected by changes in the age of giving birth," Hennessey said.
As discussed on RNZ's podcast The Detail, fertility rates are declining around the world, as more women are educated to higher levels and in employment, combined with access to contraception.
