Pacific countries that have easy access to New Zealand stand out in the region as having particularly "shaky and vulnerable" populations, says Waikato University demographer Professor Ian Pool.
Professor Pool said an examination of age pyramids provided by the Secretariat of the Pacific Community in Noumea showed Niue, Tokelau and the Cook Islands had very unstable populations.
The people of all three countries have free access to New Zealand because of historical connections.
Niue and the Cook Islands self-govern in free association with New Zealand and Tokelau is a non-self-governing territory of New Zealand.
Professor Pool said in Niue's case, the country of only about 1200 people had just 14.9 per cent in the labour force entrant age, between 15 and 24 years.
"That is very small and it is critical for development."
Worldwide the percentage of populations in that category would be about 20 per cent, he said.
Professor Pool said Niue's profile was similar to Tokelau (14.8 per cent) and the Cook Islands (15.6 per cent) and the three were probably similarly affected by out-migration to New Zealand.
He said Niue had a low number of children aged under 15, about one third of the tiny population, similar to the Cook Islands and Tokelau.
Of concern was that both Niue and the Cook Islands had negative growth rates, meaning they were losing people, compared with all other Pacific countries which had positive growth rates.
Tokelau showed little change in population size since 2001.
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The combined population of the seven smallest Pacific Island countries and territories (51,800) was about equal to the combined population of Vanuatu's two towns.
These problems likely aren't solvable, at least not when populations in the Pacific islands want First World standards of living and see relatively little prospect of achieving these at home, and do see that the only thing keeping them from mass consumist prosperity (and, perhaps, more open and diverse societies than their societies are birth) is the cost of the plane ticket and assorted other relocation and startup expenses. Absent an exceptionally strong commitment to their insular homeland, why would a Niuean (or a Tokelauan, or a Cook Islander) stay? Tonga and Samoa are both independent states, true, and in theory one would expect that this independence would discourage emigration, but in actual practice as many Tongans and Samoans live outside their archipelagic homelands as inside. Barring remarkable exceptions like Singapore, all small islands can expect to see massive emigration, independent or no.