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Opinion: Our world — 8 billion and counting

On Tuesday, world population will hit 8,000,000,000. Demographers have been using “billion” as the watershed for population growth since about 1960 when Paul Ehrlich (and his uncredited spouse Anna) wrote “The Population Bomb,” a slim book that drew worldwide attention to the myriad problems that are caused by rapid population growth. But even before that provocative publication, Kingsley Davis published “Human Society” (1949), in which he described the growth of human population as “a long, thin powder fuse that burns slowly until it hits the charge, and then it explodes.”

To put this in perspective, it is helpful to know that when Davis’ book was published, world population was about 2.5 billion, and when the Ehrichs’ book came out, it was about 3 billion. Most scholars in the field say that the “charge” of which Davis wrote was the Industrial Revolution, starting around 1750. But I think the “explosion” was really the nineteenth century, and I’ve been studying demography and writing about it (Introduction to Sociology, 1972, 1975, 1979, 1984, 1986; Global Social Problems, 1996, and California’s Social Problems, 1999, 2002) for half a century.

The population explosion

Before the Industrial Revolution, the world was agrarian. Most people in the world lived and worked on farms. In less economically developed countries, people did subsistence farming; that is, farming to feed themselves. The rise of industry brought people to cities, and many subsistence farms became commercial farms, supplying food to urban dwellers.

On the farm, children are an asset. Having many children provided future farm labor and security for parents in their old age. In the city, many children are a liability. The literary works of social critics, like Charles Dickens, often centered on workhouses, like the “orphanage” that is described in “Oliver Twist.” When urban parents had more children than they could afford, they’d send one or more to a workhouse to be cared for while they were put to work on long shifts with inadequate food and little or no education.

But city life also had good conditions for many people, including less strenuous work, fewer debilitating accidents, and longer life expectancy. So, as life expectancy increased, and death rates declined, a persistent high birth rate brought about unprecedented population growth. Over time, city folk realized that they didn’t need to have many children as fewer babies and mothers died during childbirth and more of their children lived to adulthood.

These perceptions and conditions allowed Europe and countries of European origin (for example, United States, Canada, Australia) to move toward completion of a process that Kingsley Davis called the “demographic transition.”

The demographic transition

The theory of the demographic transition posits that, for hundreds of thousands of years, the entire human population of the world grew very slowly because extremely high birth rates were offset by equally high death rates. So, 50 births per thousand population annually were matched by about 50 deaths per thousand. Therefore, the rate of growth was zero.

During the first century of the Industrial Revolution, birth rates remained relatively high, perhaps 30 to 45 per thousand, but death rates started to decline, maybe 15 to 20 per thousand, yielding a rate of growth between 1.5 and 2.5 percent per year. A population with a growth rate of two percent will double in number in 35 years.

Using our “watershed billions,” here’s what happened. It took from the beginning of human time (however you want to figure that is okay with me) until about 1830 until world population reached one billion people. Then, it took only a century for population to double. So, in 1930, world population was about 2 billion. Then it took only 30 years to add a third billion, and that’s what sparked the publication of “The Population Bomb.” Just 15 years later (1975), we hit four billion. Twelve years later (1987), five billion. Eleven years after that (1998), 6 billion.

Completing the transition

Throughout the last half of the twentieth century, there was a concerted effort on the part of the economically developed countries of the world to slow population growth around the globe. This was intensified especially after several countries had satellites circling the earth in orbit, and world leaders and policy makers could visually perceive how finite our planet is.

As the reality of climate change began to manifest itself in such observable phenomenon as long heat waves, ice melts, severe storms, deforestation, and overcrowding, countries that were economically advanced as well as newly industrialized countries began to lower their birth rates. In most cases, this was a voluntary decision based on economics, but in some cases (especially China) it was mandated by the government (for example, China’s one-child policy or India’s state-sponsored sterilization).

By the beginning of the 21st century, every country of Europe or European origin was at, nearing, or below zero population growth. Yet, it took 13 years to add the seventh billion (2011). Although China has officially ended its one-child policy, families continue the practice of having only one or two children.

According to the Population Reference Bureau, China, Thailand, and Ukraine (all previously countries that added significantly to their populations each year) are projected to have smaller populations by 2050 than they have now. Population in Europe will stabilize and then shrink. The United States, which has stable low birth and death rates like European countries continues to grow because of immigration. But for all intents and purposes these countries have completed the demographic transition.

Still, world population is projected to reach about 10.5 billion people before the end of this century because of the rapidly growing countries of sub-Saharan Africa and the Middle East. Collectively, 42 percent of the population in the countries of sub-Saharan Africa is under 15. That means this large slice of the population pie is entering or will in the future enter the reproductive years. And, in the countries of Somalia and Chad, women, on average, have 7 children. So, despite the gains that have been made, the “population bomb” continues its explosion.

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Jim Glynn is Professor Emeritus of Sociology. He may be contacted at


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