New Zealand's population would balloon to 11 million without migration rules - survey

If anyone in the world was allowed to live wherever they wanted, New Zealand's population would jump to 11 million virtually overnight.

A new survey has found that if every country opened its borders, New Zealand would experience the greatest percentage increase in population in the world.

Gallup interviewed nearly 500,000 people in 152 countries between 2015 and 2017, asking them where they'd live if they had a choice. The numbers were crunched to create a Potential Net Migration Index (PNMI) for each country - how much their population would increase or decrease by - and New Zealand came out on top with a PNMI of 231 percent.

Singapore came in second with a boost of 225 percent, with Iceland, the UAE and Switzerland rounding out the top five (208, 204 and 187 percent respectively).

New Zealand came in second when only people with at least four years' education were counted, which Gallup called the Brain Gain - a boost of 333 percent. Northern Cyprus would have the biggest Brain Gain, an increase of 432 percent, with Iceland, Spain and Singapore rounding out the top five (296, 187 and 185 percent respectively).

Gallup world map migration
Dark green countries will rise in population, which lighter countries will shrink. Photo credit: Gallup

But the young wouldn't flock to New Zealand in such great numbers, if given the chance. New Zealand's Youth score was 222 percent, putting us 10th in that category, which was topped by Iceland on 451 percent. Other countries the youth would rather move to include Singapore (410 percent), Australia (378), Switzerland (372) and Kuwait (349).

"Adult populations would still only continue to grow in North America, Europe (in both the European Union and non-EU countries), and Australia, New Zealand and Oceania if everyone moved where they wanted," Gallup said.

In contrast, Ebola-hit Sierra Leone would lose more than two-thirds of its population in a migration free-for-all, with a PNMI of minus 70 percent, and even more of its youth - minus 78 percent.

Other countries that would almost cease to exist include Haiti (minus 63 percent), Liberia (minus 60) the Democratic Republic of the Congo (minus 50 percent) and Nigeria (minus 57 percent).

Sierra Leone, El Salvador, Guinea, Congo and Albania would suffer the biggest brain drains.

Most of the countries that have said they won't be signing the UN's controversial global migration pact, fearing an influx of refugees, would actually lose population, Gallup said.

In 2009, New Zealand had the third-highest PNMI behind Saudi Arabia and Singapore. Sierra Leone also went from third to first, in the list of countries people want to leave.