As I have studied various public policy issues, I have become a devotee of the adage that "demographics are destiny." I have become particularly interested in population growth because it is such a critical element of so many of the public policy issues we face.
During most of our lifetimes, there has been dramatic changes in the rate of population growth. It will be an issue that will affect virtually every aspect of the lives of future generations. And yet I find few are even aware of what has already occurred, or of what is likely to occur in the future.
When I was a freshman in college I read Ann and Paul Ehrlich's iconic book, The Population Bomb. In it they made the argument that the world population was growing geometrically, but production, especially food production, was increasing arithmetically. They predicted massive worldwide famine and wars over resources. Their prediction was foreshadowed by Thomas Malthus, whose Essay on the Principles of Population, published in 1798, came to basically the same conclusion.
Of course, the Ehrlichs and Malthus were both wrong. They were wrong, in part, because they underestimated innovation in agricultural production, particularly the work of Norman Borlaug that sparked the Green Revolution. But they were also wrong because population growth suddenly began to drop.
Researchers estimate the world's population in 10,000BCE was about 2 million. For the next 11,500 years, the world's population grew at a snail's pace, generally less than one-tenth of a percent annually. But around 1400, the population began to climb. By the time Malthus was writing, the growth rate had risen to about .6%, which will double the population in about 100 years. Coincidentally, the world population first hit one billion about the time Malthus was writing.
But in the early part of the 20th century, the growth rate shot up like a rocket, reaching over 2% annually by the early sixties. At 2% growth rate, population doubles every 35 years. Starting with a world population of about 1.6 billion in 1900, it more than doubled twice in the 20th century, topping 6 billion by 2000. When you graph the world population from 10,000BCE it looks like this:
No wonder the Ehrlichs freaked out and declared a population bomb was going off - because it was. But then almost as fast as the growth exploded it be began to subside. It has already dropped by half and demographers expect it to continue drop. The consensus projection is that the population will top out at around 11 billion toward the end of the century. Some demographers think decline in the growth rate will even be steeper in the near term. The most likely case after 2100 is a long-term, slow decline in the world's population.
Of course, there is significant variation between different countries and regions. For the most part, population growth is falling more rapidly in more developed countries. The US is a notable outlier because we still have a relatively liberal immigration policy, at least compared to the rest of the world, and lots of people want to come here. As a result, the US projections are on par with the world projections when we might otherwise expect it would be on the low end.
Of course, the demographers could be wrong. Projecting trend lines indefinitely into the future is one of the great follies of prognostication. But a future in which population growth is declining is a widely held consensus and there are many reasons to believe the projection is likely to hold.
One of the most important factors appears to be the correlation between women's educational attainment and fertility rates, i.e., the more education a woman receives, the fewer number of children she is likely to have during her life. This is a chart from a Population Connection based on one recent study.
And women's educational attainment is rapidly rising all around the world. So, there is good reason to believe the fertility rate will continue to fall and the population growth rate with it.
If the growth in population does decline as projected, the consequences are profound for our children and grandchildren. There are certainly some advantages, most notably there will be less pressure on natural resources.
But there will also be challenges. The basic formula for GDP growth is population plus productivity growth. With population growth at or near zero it will be hard to generate robust economic growth. Also, the average age will increase dramatically, creating even more problems for retirement programs like Social Security and Medicare. Healthcare costs will also continue to climb as a result. Curing diseases that are the drivers of elder healthcare costs, like Alzheimer's, will be imperative. I'll be writing more on this in the near future.
Finally, these numbers should also give us all pause when we hear rosy predictions about growth in any context. I always roll my eyes when some chamber-of-commerce booster confidently predicts Houston and Texas are going to double in size in the next 30 years. Maybe they will, but I would take those predictions with a huge grain of salt.
