Ten Billion of us in 2100 - U.N. World Population Prospects

A very lightly covered recent story was the release of the United Nations "World Population Prospects: The 2010 Revision" report in early May.  This fascinating study gives us some insight into how our world will look in the future and how population distribution will change over the next 90 years.

On with the data.  Over the short term, the United Nations projects that the world's population will reach 7 billion people by October 31st of this year.  Using their medium variant of population growth, the United Nations projects that the world's population will reach 9.306 billion by 2050 and 10.124 billion by 2100.  Here is a chart showing their population projections using the medium variant which is defined as the variant where the fertility rate in all countries of the world converges to the replacement level:

Much of the population increase is projected to come from high-fertility countries, 39 of them in Africa, nine in Asia, six in Oceania and four in Latin America.  According to the study, very small variations in fertility rates can produce major changes in population over long periods of time.  For example, in the high projection variant where fertility increases to a mere one-half child over the medium variant (the replacement level of fertility), the world's population will reach 10.6 billion in 2050 and 15.8 billion in 2100.  In the low projection variant where fertility decreases to just one-half child below the medium variant, the world's population will reach 8.1 billion in 2050 and will decline over the next 50 years to 6.2 billion in 2100.  I find it rather amazing how having one-half child more or less can have such a massive impact on the world's population over a 90 year period.

Today, 42 percent of the world's population lives in low-fertility countries where women are not reproducing enough to ensure that they have at least one daughter that survives to the age where she will procreate.  An additional 40 percent of the world's population lives in intermediate-fertility countries where, on average, women have between 1 and 1.5 daughters and the remaining 18 percent of the world's population lives in countries where an average woman has more than 1.5 daughters.

Low-fertility countries include (among others) Japan, Canada, Russia, Australia, China, Japan, Brazil, Chile and all of the European countries except Iceland.  Medium-fertility countries include the United States, India, most of South America, northern and southern Africa, India, Turkey and Saudi Arabia among others.  High-fertility countries include most of the countries in central and sub-Saharan Africa, Pakistan, Afghanistan, Syria, Palestine, Syria and Yemen.

Here's an interactive map that you can use to see how fertility rates change with time.  I've taken one time slice from the present to show how sub-Saharan Africa has by far the highest fertility rates in the world today:

Obviously, the highest population growth potential in the future is in the high-fertility countries.  Between 2011 and 2100, using the medium variant projections, the population of the high fertility countries will more than triple from 1.2 billion to 4.2 billion.  Over the same time period, the population of the intermediate-fertility countries will increase by only 26 percent from 2.8 billion to 3.5 billion while the population of the low-fertility countries will decrease by 20 percent from 2.9 billion to 2.4 billion.  Here is a graph showing the population projections for each fertility group of countries:

Note that the populations of the low and medium-fertility countries peaks before the end of the century and then declines while the population of the high-fertility countries continues to rise well past the year 2100.  A prime example of population decline is found in the case of China.  China's current population of 1.33 billion is expected to rise to a maximum of 1.4 billion people around the year 2030 and then decline steadily because of their low fertility rate.  On the other hand, India which is a medium-fertility country, will see its population peak at 1.718 billion in 2060, making it the world's most populous nation in history.    By the year 2100, the low and medium-fertility countries will see their populations decline at about 0.3 percent per year in sharp contrast to the high-fertility countries which will still see population expansions of approximately 0.5 percent per year.

The growth in population will have a massive impact on the world's economy, especially among the world’s developing nations.  Much of the unrest in the Middle East in recent months can be attributed to a very high birthrate and declining child mortality rates in the 1970s and 1980s.  A large cohort of young adults in their 20s and 30s are now unable to support themselves because they cannot find meaningful employment.  This is certainly the case in Egypt where, despite the fact that many younger adults are university educated, they cannot find jobs that will allow them to start their own families.

As well, many people are skeptical of the very idea of "peak oil" and are most certain that the world's oil explorers can keep finding, developing and producing ever greater quantities of oil.  If the United Nation's medium variant projection is, in fact, correct, the 80 to 100 million barrels of oil per day that the world may produce over the next 25 years, will be insufficient to satiate the needs of nearly 9 billion people unless alternatives are found.  On top of the energy issue, the world has a finite area of arable land; should the population reach the 10 billion mark, more than 40 percent above today's level, my suspicion is that without massive scientific intervention, the production of food will have long past fallen short of meeting everyone's need.  It will be interesting to see if Malthus is proven correct and that increases in food production are arithmetic meaning that eventually the world's population will reach the point where it can simply no longer be fed.

The world is going to be a very different place in 2100!