That's one of the themes in an article in the Times today on immigration in Southern Europe, where populations are generally older than they are elsewhere due to low fertility.
You might call that a "pull" factor, a characteristic of countries like Spain and Italy that pulls in immigrants. Another pull factor might be domestic political progressivity.
There also are "push" factors, characteristics of sending countries and their emigrants. For example, Southern Europe is closer to developing countries where incomes are lower, like the U.S. is close to Mexico. Southern Europe shares languages and cultures with many developing countries. (The reason? Past outmigration of Southern Europeans to those places! And not always in the most peaceable of manners.)
The upbeat tone of this article contrasts distinctly with coverage of the recent tragedies in South Africa, where dozens of immigrants have been killed by bands of angry South Africans.