Are we running out of room? This is a key question when assessing the impact of global population change, and your intrinsic feeling about the answer may vary based on your country or even city of origin. Myself, Im from Canada we have roughly 11% the US population spread over 102% the physical space. To me, someone who has to drive at least 10 hours East (10 fastdriving hours) to get to the nearest major metropolitan city, the idea of running out of room is a bit odd. To someone living in Tokyo? Less so.

New research from the United Nations tries to projectoverall global trends, however, and it makes thealarming prediction that the world population will reach 11 billion by 2100. Most of that growth will come in areas that still enjoy lower population density such as Africa, which is projected to explode from 1 to 4 billion people.

Population is an interesting problem for statisticians, in that projecting its changes on the large scale requires that you think about your data points (people) as both data points and people. If you think of the actors of population change (people) too literally as people like yourself, you act naively and make bad predictions based on an incorrect understanding of their incentives; this has been the bane of birth control in the third world, as reality has challenged the assumption that that all poor women would necessarilychooseto limit the number of children they have, when given the chance. On the other hand, ignoring the human aspect of these global issues leads to even moreunproductive strategieslike the evil and unscientificschemes of old-school eugenics.

The top panel shows total world population projected to 2100. Dotted lines are the range or error, while shaded regions are the uncertainties. The darker shading is the 80 percent confidence bars, and the lighter shading shows the 95 percent confidence bars. At the bottom are the population projections for each continent.

In general, the solution to ballooning population isnt complex, its just difficult: fix world poverty. Across the board, by far the best predictor of a populations birth rate is its affluence; as a people become progressively more comfortable generation over generation, more likelyto be happy with what they see whenthey focus on their own life experience, the fewer children they have. Bringing it back to my native Canada, the birth rate for born Canadians has fallen well below replacement, and our population is only sustaining itself thanks to immigration from countries that still breed i.e., countries that are or were recently very poor.In line with this thinking, the report predicts that the now-ascendant Asian continent will plateau in population and grow from todays 4.4 billion to only about 5 billion by the centurys close. Europe,North America and Latin America are all predicted to stay under a billion people a-piece.

This study used sophisticated analytical techniques to draw some (hopefully) reliable predictions from raw data about fertility and mortality. Thats basically all these studies are doing: adding up the people wholl probably be born and the people wholl probably die, with a bit of accounting for how the living will move around the world over that time period, and youve got your number. By bringing some hard data into the conversation the team tried to give us a margin of error, calculating an80 percent probability that by2100 the world will be home to between 9.6 billion and 12.3 billion people.

Of course, any prediction looking fullyeighty-six years into the future has to be taken with a grain of salt. Global climate change could throw virtually every assumption in this paper into the garbage heap. Given breakthroughs in energy production and agriculture, we could very plausibly see a population of 50 billion, and given breakdowns in the same areas we could inherit a sparsely populated hell-world. We could end up adding the Moon, Mars, or beyond to our list of inhabitable areas. We could invent immortality and end up issuing licenses to bring a finite number of new, permanent people into the world. Remember that this paper looks ahead almost a hundred years; perhaps by then well all be plugged into a neural meta-network and physical reproduction will be a quaint and mildly disgusting idea.

Frankly, these studies mean more for the trends of today than for the realities of tomorrow, showing us the path were on so that we may intentionally step off it and onto another.

Now read: Roadmap to physical immortality: The end of death in 7 easy steps

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Earth has an 80% chance of hitting 11 billion people by 2100