The Limits To Population Projections

Aurora, Cassandra, and Bryson

Grandchildren Aurora, Cassandra, and Bryson

I am intrigued by predictions of calamities that never materialized. For example, in the five decades leading up to the year 2000, I have lived through predictions of mass starvation, nuclear annihilation, and an ice age.

In 1972, The Club of Rome published a book entitled The Limits To Growth. In the foreword, on page 11, the authors identified “the five basic factors that determine, and therefore, ultimately limit, growth on this planet,” namely:

  1. Population
  2. Agricultural Production
  3. Natural Resources
  4. Industrial Production
  5. Pollution

“Super”-exponential Growth

In this post I am concerned only with population. Particularly the predictions the authors of The Limits To Growth made about population. The book goes into detail about exponential growth in general and as it applies to population:

In 1650 the population numbered about 0.5 billion, and it was growing at a rate of approximately 0.3 percent per year. That corresponds to a doubling time of nearly 250 years. In 1970 the population totaled 3.6 billion and the rate of growth was 2.1 percent per year. The doubling time at this growth rate is 33 years. Thus, not only has the population been growing exponentially, but the rate of growth has also been growing. We might say that the population growth has been “super”-exponential; the population curve is rising even faster than it would if growth were strictly exponential. (“The Nature of Exponential Growth,”The Limits To Growth, 1972, 34)

Clearly, “super”-exponential sounds very frightening. Indeed, of sufficient concern to cause governments to panic and adopt policies they would not normally endorse.

Intriguingly, in 1972, when “The Limits To Growth” was published, the growth rate of population was already in decline. Since that year the population growth rate has continually decreased to a rate that is almost half of the peak.

14.4 Billion People by 2030

Another warning from the book:

…we can look forward to a world population of around 7 billion persons in 30 more years [in the year 2000]. And if we continue to succeed in lowering mortality with no better success in lowering fertility than we have accomplished in the past, in 60 years there will be four people in the world for every one person living today. (The Limits To Growth, 38)

Taking the population as of 1970, which was 3.6 billion, and multiplying by 4, we arrive 60 years hence in 2030 with a predicted population of 14.4 billion people.

Now, using numbers from the International Institute for Applied Systems Analysis (IIASA), let us see where the population was in 2000 and look at projections to the year 2100. I am using the IIASA estimates because they closely align with the United Nations medium variant but go beyond 2050.

Population Growth Chart and Table

World Population Growth

Year Population Year Population
2000 6.12 2050 8.75
2005 6.51 2055 8.85
2010 6.82 2060 8.87
2015 7.17 2065 8.90
2020 7.51 2070 8.89
2025 7.79 2075 8.87
2030 8.05 2080 8.85
2035 8.26 2085 8.72
2040 8.47 2090 8.62
2045 8.63 2095 8.50
2100 8.39

Population in billions

Conclusions

Notice that the 2000 population prediction was off by one billion less. The 14.4 billion forecast in 2030 will not be reached with less than 19 years left. The current IIASA projection is for a population peak that is just shy of 9 billion by 2068. Thus the prediction from The Limits To Growth will come up short by a huge 5.4 billion people.

Granted, I am using a current projection to discredit a past projection. However, the record so far is to overestimate population growth. For example, China’s population is projected to peak at less than 1.4 billion in 2026, both earlier and at a lower level than previously projected.

I expect to see further revisions downward in the projections of population growth. Fertility rates have been falling for over sixty years and demographic momentum will shrink the world’s population just as quickly as it contributed to rapid growth.

We must not let outfits such as The Club of Rome dictate to governments unwise population policies based on dubious and inaccurate predictions of the future.

External Articles

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Comments

  1. Good post. A current projection to discredit past projections is ironic, I guess. In any case, we can see that currently, past projections were wrong.

    Maybe it’s not a scare of total numbers, but their allocation (location). For example, this post analyzes growth in cities and metropolitan statistical areas:
    http://www.urbanophile.com/2011/03/17/metrocounty-census-results-so-far-plus-a-brief-look-at-jobs/

    • Why I am interested in these projections is that over the years I have noticed that population forecasts all seem to err on projecting population increases that turn out to be too great. This can turn a small problem into a supposedly large one, and this brings about undesirable public policies unnecessarily.

      I believe that is currently happening with global warming. Create such a panic by overstating the problem that the majority have to suffer a decreased standard of living, through such things as a carbon tax, for no good reason.

      When most of us live in large urban areas we can get the impression the earth is vastly overpopulated whereas it is not. Is that what you mean by allocation?

      It is interesting to see the growth in the west from your link.

      • I understand what you are saying, and I’m not really saying anything to the contrary. Perhaps population growth is hard to dispute when all of our big cities are still seeing double digit percentage growth decade after decade. There isn’t any real overpopulation, by any means, but you can see why it seemed that way in decades past.

    • 25% decline in population in Detroit.
      http://www.nytimes.com/2011/03/23/us/23detroit.html

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