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Population Growth

Perhaps less noticeable in the short lifespan of an individual is the explosion of population. But historically this change is profound: There are far more humans living now than at any point in the past. As was discussed in the History section, the number of people alive has doubled several times since fossil fuels allowed humans to grow more food and improved hygiene and medicine allowed them to live longer.

Population Myths

The UN believes there are already seven billion humans alive today. At the current pace another billion are added to that total every 12 years. This population growth has been driven by a huge decline in death rates, as modern medicine raised the average life expectancy, and lowered the infant mortality rate. Regions currently industrializing have shown dramatic improvements in life expectancy: in the 1950s people in Latin America, Asia and Africa lived on average 51, 42 and 39 years respectively. Today Latin Americans tend to live past age 70 and Asians into their mid-60s. Africa still lags behind, at just 52 years life expectancy, largely because of the slow pace of industrialization, and the ongoing AIDS epidemic.

The low death rate, combined with a consistently high birth rate is called the demographic transition by demographers. All states undergo it as they gain access to more energy and begin to industrialize. It is caused by a drop in death rates and infant mortality rates, while the birth rate takes some time to level out, leading to a population boom. Historically this transition tends to take about a century.

Once a state has become industrialized its population begins to stabilize, as people have fewer children. While the death rate will continue to remain low, the fertility rate will fall to equilibrium with, or below, the replacement rate of 2.1 children per woman. There are two main drivers behind this. The first is the desire of parents to limit the number of children they have. This is usually because of the increased cost of raising children and the fact that women are often more interested in pursuing careers of their own in an advanced economy. They are able to do this because of the invention and widespread use of birth control. The second driver behind falling fertility rates is government intervention. Many developing states see slowing down population growth as an imperative and take measures to act on this. These range from China's One Child policy, to various tax incentives and family planning programs.

The demographic transition and its impact upon world population.
The demographic transition and its impact upon world population.

The first countries to industrialize have completed the demographic transition. Europe (1.4 children per woman) and Japan (1.37) are prime examples. Canada's is only slightly higher, at 1.63, meaning that without immigrants, Canada's population will begin to shrink in the decades ahead. Nevertheless these population declines will be small, and countries tend to have vastly larger populations at the end of a demographic transition than they did at the beginning (England= ~7.7 million in 1791 to 62 million in 2011).

Many countries are still midway into the demographic transition, or just barely beginning it, meaning that the world's population growth, though slowing, is expected to continue for decades to come. The UN projects that world population will peak in 2075 at 9.22 billion, with the vast majority of the growth coming from China, India, the Middle East, Latin America, and (especially) Africa. Fully 99% of the increase in population in the next forty years will be accounted for in developing countries. The demographic transition is a powerful force indeed.

These projections of course assume a growth in energy availability to feed these new mouths, in addition to allowing people in developing countries to use more energy per capita. This is by no means assured.

Population Growth over human history.
Population Growth over human history.

Much ink has been spilled over the consequences of a vastly higher population than ever before in human history. It is certainly true that with our current lifestyles and technologies there are already too many people. One widely cited paper written in 1992 wrote:

Given current technologies, levels of consumption, and socioeconomic organization, has ingenuity made today's population sustainable? The answer to this question is clearly no, by a simple standard. The current population of 5.5 billion is being maintained only through the exhaustion and dispersion of a one-time inheritance of natural capital (Ehrlich and Ehrlich 1990), including topsoil, groundwater, and biodiversity. The rapid depletion of these essential resources, coupled with a worldwide degradation of land (Jacobs 1991, Myers 1984, Postel 1989) and atmospheric quality (Jones and Wigley 1989, Schneider 1990), indicate that the human enterprise has not only exceeded its current social carrying capacity, but it is actually reducing future potential biophysical carrying capacities by depleting essential natural capital stocks.

Of course one cannot blame these trends purely on the numbers, as people in different parts of the world live drastically different lifestyles. Those in developed countries use up far more of these "natural capital stocks" than those in the developing world, and Canadians are especially egregious offenders in this regard. In 20 years since this paper was written there has only been an amplification of these trends. Climate change, the subject of another later article, threatens to push them faster and beyond anyone's control.

Energy Inequality Article


Bongaarts, John. 'Human Population Growth and the Demographic Transition.' Philosophical Transactions of the Royal Society: Biological Sciences, Volume 364(1532); October 27, 2009. Accessed June 3, 2012.

'Fertility rate, total (births per woman)." World Bank. 2011. Accessed June 3, 2012.

'Population and the Industrial Revolution.' Economic History Society. Accessed June 3, 2012.

'Population at 1st January.' Eurostat, European Commission. Accessed 2012. June 3, 2012.

'World Population to 2300.' UN Department of Economic and Social Affairs: Population Division. (New York: United Nations, 2004), p. 5. Accessed June 3, 2012.