A very interesting article by a New York Times writer provides a theory for how nations should adapt in the coming decades to population growth. It is in response to a new study that found that, unlike previous studies on the same topic, the population of the Earth isn't peaking. In fact, the study projects that by 2100, it is conceivable that we will have 12.3 billion on the planet (the current population is 7.2 billion).
Previous estimates believed that a drop in the fertility rate in Africa would lead to a plateauing effect on the Earth's population. But the expected drop in the fertility rate is progressing much slower than many experts believed. The newest study makes the case that the world population is due to expand at least through the century, and maybe beyond.
But what the source article we link to asserts is that with all of these people on the planet, immigration will only become a more pressing and immediate concern for countries. And how those countries adapt their immigration laws and accept people from other countries will determine how successful (financially or otherwise) those countries will be in the future.
In other words, keeping your doors closed and restricting people from entering your country is unlikely to help the country in question.
Whether this ends up being true or not is anyone's guess. There is a lot of speculation involved here -- there's no denying that. But it is an interesting idea, and one that is worth pondering.
Source: New York Times, "A Strategy for Rich Countries: Absorb More Immigrants," Tyler Cowen, Nov. 8, 2014