Five years ago I wrote a piece called, Technophysio Evolution and Demographic Transition, explaining the dynamics and trends of global population growth and decline. Slate has and excellent article explaining the Demographic Transition Model.
Research suggests we may actually face a declining world population in the coming years.
The world’s seemingly relentless march toward overpopulation achieved a notable milestone in 2012: Somewhere on the planet, according to U.S. Census Bureau estimates, the 7 billionth living person came into existence.
Lucky No. 7,000,000,000 probably celebrated his or her birthday sometime in March and added to a population that’s already stressing the planet’s limited supplies of food, energy, and clean water. Should this trend continue, as the Los Angeles Times noted in a five-part series marking the occasion, by midcentury, “living conditions are likely to be bleak for much of humanity.”
A somewhat more arcane milestone, meanwhile, generated no media coverage at all: It took humankind 13 years to add its 7 billionth. That’s longer than the 12 years it took to add the 6 billionth—the first time in human history that interval had grown. (The 2 billionth, 3 billionth, 4 billionth, and 5 billionth took 123, 33, 14, and 13 years, respectively.) In other words, the rate of global population growth has slowed. And it’s expected to keep slowing. Indeed, according to experts’ best estimates, the total population of Earth will stop growing within the lifespan of people alive today.
And then it will fall. ...
... Why is this happening? Scientists who study population dynamics point to a phenomenon called “demographic transition.”
“For hundreds of thousands of years,” explains Warren Sanderson, a professor of economics at Stony Brook University, “in order for humanity to survive things like epidemics and wars and famine, birthrates had to be very high.” Eventually, thanks to technology, death rates started to fall in Europe and in North America, and the population size soared. In time, though, birthrates fell as well, and the population leveled out. The same pattern has repeated in countries around the world. Demographic transition, Sanderson says, “is a shift between two very different long-run states: from high death rates and high birthrates to low death rates and low birthrates.” Not only is the pattern well-documented, it’s well under way: Already, more than half the world’s population is reproducing at below the replacement rate. ...
... One of the most contentious issues is the question of whether birthrates in developed countries will remain low. The United Nation’s most recent forecast, released in 2010, assumes that low-fertility countries will eventually revert to a birthrate of around 2.0. In that scenario, the world population tops out at about 10 billion and stays there. But there’s no reason to believe that that birthrates will behave in that way—no one has every observed an inherent human tendency to have a nice, arithmetically stable 2.1 children per couple. On the contrary, people either tend to have an enormous number of kids (as they did throughout most of human history and still do in the most impoverished, war-torn parts of Africa) or far too few. We know how to dampen excessive population growth—just educate girls. The other problem has proved much more intractable: No one’s figured out how to boost fertility in countries where it has imploded. Singapore has been encouraging parenthood for nearly 30 years, with cash incentives of up to $18,000 per child. Its birthrate? A gasping-for-air 1.2. When Sweden started offering parents generous support, the birthrate soared but then fell back again, and after years of fluctuating, it now stands at 1.9—very high for Europe but still below replacement level.
The reason for the implacability of demographic transition can be expressed in one word: education. One of the first things that countries do when they start to develop is educate their young people, including girls. That dramatically improves the size and quality of the workforce. But it also introduces an opportunity cost for having babies. “Women with more schooling tend to have fewer children,” says William Butz, a senior research scholar at IIASA. ...