small_375127836How many people are we today?
We are (roughly) 7,1 billion people sharing 1 Earth (May 2013, according to Worldometers web site, http://www.worldometers.info/world-population/ ).

You can check out how much that really is by looking at this web site: http://www.7billionworld.com/ You and me both are there somewhere!

Some historical perspective: We were about 1 billion people in the early 19th century, so in the last 200 years or so, we have gone from approximately 1 billion people to 7 billion people.

photo credit: Arenamontanus via photopin cc

How many people will we be in the near future?
According to Worldometers, the population is still increasing but the rate that it’s increasing with has decreased since the late 1960s. Confusing? Well, it means that the population still grows, but not as fast as before.

Some estimates of future population: :

  • 2025: 8 billion     8,1 billion
  • 2050: 9,2 billion  9,6 billion
  • 2100: 10 billion  10,9 billion

The strikethrough figures are from the Worldometers web site and pulled May 2013, based on the United Nations 2010 projections. The updated figures are from June 2013 and the report ”World Population Prospects: The 2012 Revision, Key Findings and Advance Tables” produced by the Population Division of the Department of Economic and Social Affairs of the United Nations.

In May 2013, Worldometers cited United Nations projections that say that the population will stabilize at 10 billion. But maybe this is oversimplifying the projections. Also in May 2013, according to Wikipedia (search for World population) the UN 2010 high projections suggested that we could be 16 billion and the low said that we could be 6 billion by 2100. The new (2012) UN high projection suggests that we could be 16,6 billion and the low projection says that we could be 6,8 billion by 2100. One should also bear in mind that the forecast relies on the fact that family planning will be used more throughout the world in the future, thus decreasing the fertility rates. If we should have the same fertility rates as during 2005 – 2010, we could have a total population near 30 billion in 2100.

Why does the UN 2012 forecast estimate a higher total poulation than before?
This new forecast estimates a higher total population than the previous one (almost a billion more in 2100 than earlier thought). Three main reasons are given for this:

  1. Fertility levels have been adjusted upward in a number of countries on the basis of recently available information. In some cases, the actual level of fertility appears to have risen in recent years; in other cases, the previous estimate was too low.
  2. Slight modifications in the projected fertility rates of some very populous countries have yielded important differences in long-run forecasts.
  3. Future levels of life expectancy at birth are slightly higher in several countries in this latest projection.

What factors affect the size of the world population?
The answer seems to be really easy, it’s basically the birth rate and  the death rate, which decide whether the world population will increase or decrease. How many babies are born and how many people die?

The birth rate can be affected by things like access to contraception, education, but also cultural differences can affect how many children you want to have.

On the other hand, the death rate can be affected by the access to clean water, food, sanitation, technology, health care and education. Diseases and natural catastrophes can of course strike and cause deaths.

It is said that every woman need  on average needs to bear about 2,1 children to replace herself and her partner. (It is more than 2 children, because of child mortality. This is being calculated based on a child mortality rate in the Western World.)

I also read this interesting article on Wikipedia about the demographic transition, which is a theory on how both the birth and death rates go from high to low as a country develops from a pre-industrial to an industrialized economic system. The Wikipedia article is partly based on a publication by Keith Montgomery from year 2000, published on the web site of University of Wisconsin – Marathon County, which I also read (links below). (Picture below thanks to SuzanneKn [Public domain], via Wikimedia Commons.)

Dtm_pyramids, largerThe theory goes that at first both birth and death rates are high, which keeps the size of the population balanced. Then as the country develops the number of deaths decline due to improvements in the areas listed above, which causes the population to grow, since birth rates still are high. The population consists of more young people than old people, a classic population pyramid.

Then the birth rate starts to go down. It seems like the reasons for this is unclear, but speculations in the articles are that in a more industrialized society, you realize that you don’t need as many children as before to sustain your personal economy and retirement, since the children you bear actually survive. Also values change, women get education and start to work outside the home. The cost of caring for each child gets higher, since the children are not expected to work until they are adults. Women who get education tend to be older when they start to have children. I think women and their partners feel that a lower number of children is ”enough” and the access to contraceptives makes it possible to control how many children to have. When the birth rate goes down, once again the population growth is balanced, but since you had a growth earlier these people get older and older. The population pyramid becomes more of a square.

If the birth rates decline even more, the population pyramid can start to resemble a circle.

But it also seems that it is very hard to predict the future. A BBC article quotes Professor Jane Falkingham: “”We’ve actually got population projections wrong consistently over the last 50 years,” says Professor Falkingham, “and this is partly because we’ve underestimated the improvements in mortality, particularly older age mortality, but also we’ve not been very good at spotting the trends in fertility.“” Another quote from the article:  “”Historically, fertility has been falling across Europe,” says Professor Jane Falkingham, director of the ESRC Centre for Population Change at Southampton University. “But actually if we look at the most recent period, the last 10 years or so, we see rises in fertility in the most advanced countries.””

As I’ve written before the forecasts are that the world population will grow in the near future and Falkingham’s statements seem to indicate that also, but who knows what the future really brings…

How old will we get?
This is of course a question no one knows the answer to on an individual basis, but there are estimates of the “life expectancy at birth”. For a list, see for example the World Factbook of CIA. I also refer to the report ”World Population Prospects: The 2012 Revision, Key Findings and Advance Tables” from the Population Division of the Department of Economic and Social Affairs of the United Nations.

The report says that “Globally, life expectancy at birth is projected to rise from 69 years in 2005-2010 to 76 years in 2045-2050 and to 82 years in 2095-2100. In the more developed regions, the projected increase is from 77 years in 2005-2010 to 83 years in 2045-2050 and to 89 years in 2095-2100…”.  “Life expectancy remains low in the least developed countries, at just 58 years in 2005-2010. Although it is projected to reach 70 years in 2045-2050 and 78 years in 2095-2100, realizing such an increase is contingent on reducing the spread of HIV and combating successfully other infectious diseases as well as non-communicable diseases.”

This means that there is much work left to do to increase the life expectancy in the least developed and developing countries! There will probably still be a difference in how long you will live, depending on where you happen to be born, but on average that difference is estimated to decrease to ten years from today’s 35-40 years.

World Population Prospects: The 2012 Revision, Key Findings and Advance Tables
The World Factbook of CIA

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