Where would the world's people live if they could move anywhere?

Gallup's "Potential Net Migration Index" is an estimation of how countries' populations would change if everyone in the world could live wherever they wanted.

After roughly 520,000 interviews in 154 countries, they subtract the number of people who would want to leave each country from the number of people who want to move there and come up with a numeric score.

Here are the results of this year's index by region:

Americas: 13

Europe: 10

Middle East and North Africa: 4

Asia : -6

(Based on aggregated surveys in 154 countries between 2010 and 2012.)

Europe's high score comes despite declines that would occur in Southern Europe. Greece, for instance, has slipped into negative territory, from +11 percent to -8 percent, since the last time the survey was taken, in 2009.

Canada and the United States are still the world's two most desirable destinations for immigrants. Canada's population would increase by 120 percent in a borderless world, America's by 45 percent.

Worryingly, that U.S. number is down significantly from 60 percent in 2009. It's still an extra 141 million people, though, or roughly the equivalent of bringing everyone in Russia into America. (The old Russia, that is. Russia's population would decline by 9 percent in this scenario.)

The biggest increase in population would be in Switzerland, which would grow by 136 percent if everyone who wanted to move there could. (They definitely can't.)