KEY POINTS:
The 2006 Census has revealed an odd dearth of young Pacific men in the country compared with the number of Pacific women.
A study into Pacific demographics showed there were 12 per cent more women recorded in the Census in the 25 to 29 years age group than
there were men.
The discrepancy can't just be put down to the so-called man drought in New Zealand, as total population figures show the number of all women aged 25 to 29 is only about 9 per cent more than men.
Dr Paul Callister, senior research fellow at Victoria University, said the Pacific figure was a bit of a puzzle but possibly partly explained by the fact that young men were more likely to be separated from the family unit and less likely to be counted on Census night.
They were also possibly more likely than women to travel back and forth between New Zealand and Pacific countries, and be away when a Census was taken.
Robert Didham, demographic analyst for Statistics New Zealand, said the possible reasons for Pacific men not fully showing up in the Census data would be complex and varied.
Mr Didham said it would be wrong to assume the men were not recorded because they were overstayers and feared giving out such information.
He said younger people were generally more likely to not fill in Census forms, a problem shared by overseas countries.
Mr Didham said not everyone correctly identified their ethnicity, although he could not say why Pacific men would be more likely to do that than women.
Higher male mortality rates could also be implicated in the discrepancy.
In younger age groups there were about 5 per cent more Pacific boys than girls and about equal numbers by 15 to 19 years.
The research showed some major differences of sex ratios within the main Pacific ethnic groups.
While in the 30-34 years age group there were 11 per cent more Samoan women than men, and 18 per cent more Cook Islands women, there appeared to be about 5 per cent more Tongan men than women.
The research said undercounts of fast-growing Pacific populations, currently estimated at 265,974, could create problems in developing social policy.
Mr Didham said the Pacific undercount was estimated at 2.3 per cent in the 2006 Census compared with a 1.4 per cent undercount for Europeans.
But the undercount for Asian ethnicities was 5.2 per cent and for Maori 3.1 per cent.
The total Census undercount in New Zealand was about 2 per cent, or 81,000 people.
The research by Dr Callister and Mr Didham also showed that Samoans continued to be the largest single Pacific ethnic group in New Zealand, but Tongans showed the strongest growth in numbers in the past five years, rising from just over 31,000 to 50,000.