WASHINGTON — Singapore, New Zealand and Saudi Arabia would see their populations triple if everyone who wants to move there were allowed to, a poll released Friday by Gallup shows.

At the opposite end of the scale, the populations of Sierra Leone, Haiti and Zimbabwe would fall by more than half if migrants were allowed to leave at will, the poll found.

Zimbabwe, where life expectancy is around 47 years and 15 percent of the population need food aid, would lose 47 percent; Nigeria — Africa’s most populous nation with a population of 152 million — and Ethiopia would each lose 46 percent, and Liberia’s population would fall by 45 percent.

For Nigeria alone, the poll findings mean that 75 million people want to leave the west African state.

Gallup researchers interviewed nearly 350,000 adults in 148 countries between 2007 and 2010 to calculate each country’s potential net migration score — the number of adults who would like to leave a country minus the number who would like to move in — seen as a proportion of the total adult population.

They found that Singapore’s population of 4.8 million would increase by 219 percent, New Zealand’s population of four million would rise by 184 percent and Saudi Arabia’s population of 26 million would soar by 176 percent if everyone who wants to come in and wants to leave, could.

Switzerland made it onto the list, which was first compiled in 2009, for the first time this year.

Some 800,000 of Switzerland’s six million citizens said they would like to permanently leave the country, while some 10 million foreigners said they would move there, given the chance.

The hefty influx of migrants to Switzerland versus the scant outflow from the Alpine country would mean its population would more than double, according to the Gallup poll.

The preferred destination of most would-be migrants is still the United States, although the already large US population — 300 million inhabitants — means that the impact is less acutely felt, Gallup said.

The United States is number 14 on the net migration list. If everyone could come into the United States that wanted to, and all those who wished to leave did, the US population would rise by around 60 percent.

At the other end of the list, many countries in Africa and Latin America showed net outflows of population — although four African countries would gain residents, the poll showed.

They are Botswana, which would see its population increase by 39 percent; South Africa, Zambia and Namibia, which would see rises of 13 percent, five percent and two percent, respectively.

Botswana, which ranked just after the United States and just above Norway on the list, is the world’s top producer of diamonds and a leading destination for high-end tourism. It prides itself on being a model of successful democracy in Africa.

At rock-bottom on the Gallup list is Sierra Leone, the west African country that is still struggling to recover from a 10-year civil war that officially ended in early 2002.

If everyone who wanted to leave Sierra Leone could, and anyone who wanted to move there did, the country’s population would plunge by 56 percent.

Haiti, the poorest country in the Americas, would lose 51 percent of its population.

“While Gallup’s findings reflect people’s wishes rather than their intentions, the implications of what could happen if these desires become reality are serious considerations for leaders as they plan for the future,” Gallup said.

Two Latin American countries besides Haiti figure in the bottom 10 of the list: El Salvador would lose 45 percent of its population and the Dominican Republic would lose 43 percent.

The lowest ranked European Union member state on the list is Latvia, which would lose around a quarter of its population of 2.3 million if migrants were allowed to come in and go out as they wished.

“High unemployment, low wages and a rising cost of living have driven many Latvians out of the country,” University of Latvia migration specialist Aija Lulle told AFP.

Latvia ranked equally with Iran, and was only marginally better than the Philippines.

– Jordi Zamora and Karin Zeitvogel (AFP)