Dunedin and Otago's once dominant Presbyterian tradition is slipping further into the past.
More people hold no religious belief in Dunedin than those who do, 2013 census data released yesterday shows.
The number of those with a religious affiliation dropped to 53,376 from 61,608 in 2006, while those who had no religion increased to 55,233 from 45,111.
Of the major religious groups, Presbyterianism had the greatest drop as people who affiliated with the denomination fell to 17,455 from 22,290 in 2006.
However, it remains easily the largest denomination in Dunedin and Otago.
While Dunedin mirrored the trend of decreasing religiosity throughout New Zealand, it and Queenstown Lakes district were two of only five territorial authorities where the irreligious outnumbered the religious.
Of those, Dunedin City had the largest population and was the least religious of New Zealand's major centres.
In New Zealand there were 2.146 million people with a religious affiliation (down from 2.271 million in 2006) and 1.635 million people with no religion (up from 1.297 million in 2006).
University of Otago associate professor of philosophy and religion Greg Dawes said it was difficult to know what caused the trend towards lower religiosity, but he believed Dunedin being a ''university town'' might be a factor.
''There's no simple correlation between education and non-belief, but ... because Dunedin is a university town there may be more people that associate as being non-believers,'' he said.
While the number of those who were religious would probably continue to decline, those who remained religious could become more galvanised in their belief.
''When the overall rate of participation in religion declines there's a tendency for those who are involved to become more committed and even more extreme in their views,'' Dr Dawes said.
Debates about issues such as teaching religion in schools and creationism could become ''lively'' as the religious population continued to decline, he said.
Hinduism, Islam, Judaism and Sikhism had moderate increases in believers, most of which could be attributed to demographic change, but the increase in Judaism was interesting, as ''Dunedin ... once had quite a significant Jewish population'', he said.
The data released yesterday also showed more people in Otago affiliated themselves with an iwi, drove more cars and earned more.
The number of people who affiliated themselves with an iwi grew to 17,838 from 16,122 in 2006. Most of that increase was as a result of 627 more people affiliating themselves with Ngai Tahu.
There was an increase in the number of people who owned one vehicle, two vehicles and three or more vehicles and a decrease in the number who did not own a vehicle.
The data also showed median household income in Otago had risen to $56,400 from $44,400 in 2006, but it was still short of the national median average of $63,800.
The number of households earning $100,001 or more was up to 14,343 from 8286.
