Some 700 million people worldwide, or more than all the adults of North and South America combined, think the grass is greener on the other side of the fence and want to permanently move to another country, a poll showed Tuesday.

Residents of sub-Saharan African countries were the most likely to want to move abroad permanently, the polls conducted in 135 countries between 2007 and this year by Gallup showed.

On average, 38 percent of the adult population in sub-Saharan Africa, or around 165 million people, said they would up stakes and head for another country if they had the chance.

The most popular destination was the United States, where nearly a quarter of the 700 million -- around 165 million people -- said they would like to settle.

In joint second were Britain, Canada and France, each being named as the preferred destination of around 45 million people.

Thirty-five million said they would go to Spain, 30 million to Saudi Arabia, and 25 million each to Australia or Germany.

The least likely to want to emigrate were Asians -- only one in 10 Asian adults said they would move to another country.

Nearly 260,000 people aged 15 years and older were surveyed, either by phone or face-to-face, for the poll, which has a margin of error of around five percent.