"Marriage and divorce are far less common than in the past."
Today's figures also show the divorce rate is falling.
The divorce rate fell in 2018 to 7.7 divorces for every 1000 estimated existing marriages and civil unions. This was the lowest rate since 1977.
The current decline continues the general decrease in the divorce rate since 2004. Last year the rate was 40 per cent lower than in 2004, when it was 12.8 per 1,000.
The number of divorces in New Zealand dropped to 7455 in 2018, the first time it was below 8000 since 1980. A law change in 1981 saw an initial sharp increase in divorces in the early 1980s.
The decreasing divorce rate coincides with a decrease in the number of children whose parents divorced. Last year, 5598 children under 17 years had parents who were granted a divorce, down from 9429 children in 1998.
Same-sex marriages were first celebrated in New Zealand in August 2013.
There were 4872 same-sex marriages between then and last December. That includes a similar number of New Zealand-resident marriages (2568), and overseas-resident marriages (2307) registered in New Zealand.
Over the past five years, the average number of same-sex marriages was around 900 a year, 3.5 per cent of the average total marriages (23,335) over this time.
The number of same-sex marriages registered in New Zealand to overseas residents decreased, coinciding with the introduction of same-sex marriages in Australia from December 2017. In 2018, 375 same-sex marriages were registered in New Zealand to overseas residents, down from the peak of 495 in 2017.