November 19, 2003
Human Population May Add 2.6 Billion By 2050

There will be 8.9 billion people on planet Earth by 2050.

It took from the beginning of time until 1950 to put the first 2.5 billion people on the planet. Yet in the next half-century, an increase that exceeds the total population of the world in 1950 will occur.

So writes Joel E. Cohen, Ph.D., Dr.P.H., professor and head of the Laboratory of Populations at The Rockefeller University and Columbia University, in a Viewpoint article in the November 14 issue of the journal Science.

In "Human Population: The Next Half-Century," Cohen examines the history of human population and how it might change by the year 2050. By then, the earth's present population of 6.3 billion is estimated to grow by 2.6 billion.


In the Science article, Cohen reports such statistical information as the following:

  • history of human population: It took from the beginning of time until about 1927 to put the first 2 billion people on the planet; less than 50 years to add the next 2 billion people (by 1974); and just 25 years to add the next 2 billion (by 1999). In the most recent 40 years, the population doubled.
  • birth rates: The global total fertility rate fell from five children per woman per lifetime in 1950 to 2.7 children in 2000, a result of worldwide efforts to make contraception and reproductive health services available, as well as other cultural changes. Encouraging as this is, if fertility remains at present levels instead of continuing to decline, the population would grow to 12.8 billion by 2050 instead of the projected 8.9 billion.
  • urbanization: In 1800, roughly 2 percent of people lived in cities; in 1900, 12 percent; in 2000, more than 47 percent. In 1900, not one metropolitan region had 10 million people or more. By 1950, one region did -- New York. In 2000, 19 urban regions had 10 million people or more. Of those 19, only four (Tokyo, Osaka, New York, and Los Angeles) were in industrialized countries.
  • poor, underdeveloped regions: b
  • population density: The world's average population density is expected to rise from 45 people per square kilometer in the year 2000 to 66 people per square kilometer by 2050. Assuming 10 percent of land is arable, population densities per unit of arable land will be roughly 10 times higher, posing unprecedented problems of land use and preservation for the developing world.
  • aging population: The 20th century will probably be the last when younger people outnumbered older ones. By 2050, there will be 2.5 people aged 60 years or older for every child 4 years old or younger, a shift that has serious implications for health care spending for the young and old.

Although it is not possible to predict how global demographics will affect families or international migration, Cohen points out that three factors set the stage for major changes in families: fertility falling to very low levels; increasing longevity; and changing mores of marriage, cohabitation and divorce.

In a population with one child per family, no children have siblings, Cohen explains. In the next generation, the children of those children have no cousins, aunts, or uncles.

If people are between ages 20 and 30 on the average when they have children and live to 80 years of age, they will have decades of life after their children have reached adulthood, and their children will have decades of life with elderly parents, Cohen also points out.

If family sizes shrink in the Middle East one consequence will be to reduce tribalism. But if life expectancy increases dramatically then the tribal bonds may continue for somewhat longer period of time due to intergenerational bonds and because the older generations who still have siblings and cousins galore will stick around longer.

All else equal, the political value of having a larger population is to make a country potentially stronger as a result of having more workers and also greater economies of scale. But the costs of crowding, pollution, and burden on the environment rises as well (and suburbs and freeways stretching as far as the eye can see is esthetically undesireable for most of us). For a country that wants to compete in terms of power and influence given that the productivity of workers varies literally by orders of magnitude it makes much more sense to have a much smaller increase in population but to make that increase be much more heavily weighted toward people who have very high economic productivity.

Productive potential is a function of innate cognitive ability, training, and motivation. A large raw increase in population decreases the amount of resources available to train each new member of a society. It is more cost-effective to add people who have much higher cognitive ability because:

  • smarter folks are faster learners and are quicker and therefore cheaper to train.
  • smarter folks can do brain work more rapidly.
  • smarter folks can do types of brain work that are beyond the ability of lesser minds.

The value of physical labor continues to decline relative to the value of complex mental work as the sum total of all knowledge increases and provides a larger body of information which can be manipulated to create economic value. But even the value of having a smarter brain may eventually be obsolesced by technological advances.

If computers become smarter than humans then the economic value of having a larger number of smarter and more productive humans will eventually pale next to value of having smart artificially intelligent computers.

Share |      Randall Parker, 2003 November 19 12:17 AM  Trends Demographic

Patrick said at November 19, 2003 10:55 PM:

I'm not sure all those Quoted Factoids are correct. For example "Of those 19 [Cities over 10 million people], only four (Tokyo, Osaka, New York, and Los Angeles) were in industrialized countries." Well I know that Seoul in Korea has well over 10 million, as does Moscow and London. They are all pretty industrialized.


Randall Parker said at November 19, 2003 11:23 PM:

Patrick, I'm skeptical. I get less than 10 million from a few different google search hits on Moscow. See for instance:

Moscow proper had a population (1999 estimate) of 8,297,900. The city's annual growth rate slowed significantly between 1970 and 1990—from 1.21 percent to .26 percent—in part because of declining birthrates.

The UN puts Moscow at about 9.3 million in 2000 and its population isn't growing rapidly.

I do find figures that do put Seoul at around 10.3 million. But London is less than 10 million and this chart gives a historical perspective on London's population.

Nancy Lebovitz said at November 20, 2003 6:21 AM:

A socially functional human being takes years of work to produce, much of it boring and/or exhausting, and as noted, decently-off people in developed societies aren't willing to do a lot of it.

The first society which figures out how to raise intellgence from mediocre to good and/or excellent wins. I wonder how the cost of developing that sort of intelligence increase compares to the expenses of keeping immigrants out.

Nick D said at March 9, 2005 4:18 AM:

You state London has a population under 10 million, yet New York is over that figure. You are comparing apples and oranges. New York city (excluding metro area) is around 8 million, London (excluding metro area) is around 7.5. The equilavent metro figures are both well over 10 million. The official London figures now state the population of over 18 million (if you check wikipedia).

So either neither NYC or London have a population over 10 million - or both do - you choose :) The same can also be said of Paris.

darren sumpton said at July 7, 2005 4:42 AM:

how much bigger is london to paris.

Freddiw said at October 21, 2005 8:32 PM:

London has a population of 16.2 million people

Freddiw said at October 21, 2005 8:32 PM:

London has a population of 16.2 million people

Nic said at June 26, 2007 12:47 PM:

Nothing like a bit of pseudo research and statistics to support a dubious proposition. People have been suggesting our physical labour requirements are to decrease 'soon' for decades, but the technology with which we are to replace human physical effort has been of lesser significance than anticipated. And what if eventually we succeed - one only has to look at the dismal states of physical prowess of the performers of many sedentary occupations who are 'intelligent' [at least in their own minds] to see this is not a positive direction for the human race. While rationales are based upon economic output we will be well and truly f^#ked

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