Dunedin has the lowest fertility rate in New Zealand.
But a University of Otago sociologist says it is not something in the water.
Surprisingly, the situation is caused by our large body of female tertiary students.
Recent subnational population projections from Statistics New Zealand revealed Dunedin city has a rate of 1.35 births per woman for the period 2007-11 - the lowest total fertility rate in the country.
Statistics New Zealand statistical analyst Richard Speirs said the projected medium variant births for territorial authorities for the period were derived by obtaining the number of registered births for the three years ending June 30, 2009, and pro-rating the figures up to a five-year period.
"For Dunedin city, this pro-ration gave a total of 6460 births for the period 2007-2011, which equates to a total fertility rate of 1.35."
The Wairoa district has the highest fertility rate, with 3.25 live births per woman.
In the period 2027 to 2031, Statistics New Zealand predict the total fertility rates will range from 1.28 births per woman for Dunedin city (very low fertility variant) to 3.12 births per woman for Wairoa district (high fertility variant).
Mr Speirs said the "total fertility rate" was the average number of live births that a woman would have during her life if she experienced "the age-specific fertility rates" of a given period.
The issue was not just affecting Dunedin, he said. The Otago region has had the lowest total fertility rate since 1995-97.
"The region has by far the lowest fertility rates in the 20-24 age group, and among the lowest for those women aged under 20 and aged 25-29 years old."
University of Otago Anthropology, Gender and Sociology Department sociologist Dr Bryndl Hohmann-Marriott said the main reason for Dunedin's low fertility rate was the large number of female students who did not want to have babies while they were at university.
To a lesser degree, the region's large non-childbearing elderly population (aged 65-plus) was also a factor, she said.
"It's not something in our water. It's about population composition."
The region's population was relatively stable, despite the student-affected fertility rate, and had been for quite some time.
The figure to keep an eye on was the national fertility rate, she said.
New Zealand's total fertility rate was projected to increase from 1.99 births per woman in 2006 to 2.11 in 2011. It was then projected to decrease to 1.90 in 2026, and then remain constant.
Dr Hohmann-Marriott said, "2.1 births per woman was the magic number.
That allows the population to keep stable. It keeps up with early mortality.
"At this stage, there is no need to worry about our fertility rate," Dr Hohmann-Marriott said.
