Sex, lies, and statistical correlation: A caveat for populationists

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The next time someone tells you that population growth has been proven to cause climate change, tell them about the academic study that ‘proves’ penis length affects economic growth

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The next time someone tells you that population growth has been proven to cause climate change, tell them about the academic study that ‘proves’ penis length affects economic growth

by Ian Angus

As regular readers of Climate and Capitalism know, Simon Butler and I have written a book on the myth that population growth is a major cause of the global ecological crisis. Too Many People? will be published in October by Haymarket Books.

Again and again, while researching that book, we found populationist campaigners citing academic studies that supposedly proved that human population growth accelerates greenhouse gas emissions, deforestation, biodiversity loss, and other forms of ecological damage.

But when we read the actual studies, we found statistical analyses that used what the pioneering environmental sociologist Alan Schnaiberg called a “two accounts” model — one set of numbers (e.g., population) is used to explain another set of numbers (e.g., pollution).

The inconvenient truth is that such a approach can only show correlation, not causation.The patently obvious fact that population and pollution grew at the same time does not prove that one caused the other.

Some of those studies were pretty simple to read and refute, but others required knowledge of sophisticated statistical techniques. Pages of computer-generated tables and graphs can be intimidating – they give the populationist argument an aura of mathematical and scientific certitude that non-specialists find difficult to penetrate.

If I ever have to do it again, rather than explaining the limitations of statistical studies, I’m just going to refer readers to an academic paper published this month by Tatu Westling of the University of Helsinki. It is simultaneously a serious statistical study, and one of the funniest academic papers I’ve ever read.

It’s called “Male Organ and Economic Growth: Does Size Matter?”

Westling tells us that although many other studies “concentrate on economic, social and political factors, these and many related treatments largely abstain from biological and/or sexual considerations. The aim of this paper is to fill this scholarly gap with the male organ.”

By detailed statistical analysis, he shows that the average size of an erect male penis “can alone explain over 15% of the variation in GDP” between countries, and that “it alone explains over 20% of the variation in GDP growth” between 1960 and 1985.

In fact, penile length “is also found to be more important determinant of GDP growth than country’s political regime type.”

The relationship is not linear – penises can be too large. “The GDP maximizing size is around 13.5 centimetres, and a collapse in economic development is identified as the size of male organ exceeds 16 centimetres.”

His overall conclusion:

“The average size – the erect length, to be precise – of male organ in population has a strong predictive power of economic development during the period. The exact causality can only be speculated at this point but the correlations are robust.”

As anyone who has read similar studies can testify, the tone of Westling’s paper is perfect. Even more important, his methodology is beyond reproach: he actually did this study, and his conclusions are backed up by five pages of graphs and tables.

But he sneaks in a few zingers:

  • “Taken at face value the findings suggest that the `male organ hypothesis’ put forward here is quite penetrating an argument. Yet for the best of author’s knowledge, male organ has not been touched in the growth literature before.”
  • “It clearly seems that the `private sector’ deserves more credit for economic development than is typically acknowledged.”

As a serious analyst, Westling is explicit about the limitations of his research:

“these findings entail one major caveat as they can only establish statistical correlations, not necessarily causalities. Hence to conclude that small male organs have driven GDP growth since 1960 is premature, however strong the correlation.”

Wouldn’t it be nice if populationist studies were as honest?

A PDF of Tatu Westling’s paper can be downloaded here.


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  • Recent studies show that 83% believe the validity of statements that begin with the phrase “Recent studies show . . .”.

  • Ian wrote: “Even more important, his methodology is beyond reproach: he actually did this study, and his conclusions are backed up by five pages of graphs and tables.”

    This has to be tongue-in-cheek. The Westling article is nothing more than a clever parody of a serious study.

    In fact, the non-seriousness of this “study” is precisely what gives it its power as a debunker of false statistical analyses. The message is: We should laugh at this study, but also laugh at the “serious” studies that are just as phony.

  • I now see the term “cum hoc fallacy” in an entirely new light….;) Thanks Ian!

  • I have been reading your debate with Saral Sarkar, and I am sorry, but much as I agree with many of your other conclusions and writings, you are wrong about population and environmental damage, and therefore, ultimately climate change. Today’s blog just leaves me cold. Not funny really. Perhaps we need not be as drastic as Arne Naess suggests; however, 7 billion people is way too many. Sure policies need to change, governing needs to be just and equal, and wealth needs to be distributed fairly. But humans are part of the environment and we have no more right than any other part to consume its resources with abandon, neglect, and selfishness. Animal populations control their own numbers — so can we. I believe the Earth will be able to survive the degradation wrought by humans — the question is will the humans? For us to survive, we must contain our numbers, slowly and fairly, but the growth must stop. Let’s strive for quality (development) not quantity.

    • Eleanor: No need to apologize. I don’t expect to convince everyone right away.

      The point of the article that you find “not funny” — and of others I’ve written on this subject — is that numbers alone prove nothing. The statement “7 billion people is way too many” is not a useful guide to action. It’s just a big number, nothing more.

      The real questions are:

      –Is environmental destruction primarily caused by the fundamental nature of our society, or by the number of people in it? Do we need to change the way we live, or just change how many of us live this way?

      –Is the problem the existence of a large number of people, or the activities of a small number of people who plunder the earth to reap private wealth?

      –Are the most destructive countries those with growing populations, or those whose populations are stable or falling?

      –Will reducing population change the grossly ecocidal nature of capitalism?

      –If capitalism remains intact, will reducing population reduce environmental degradation in any significant way?

      –Will campaigning for reduced population help build a powerful green movement, or will it alienate us from our most important allies, and divert the movement away from its most important tasks?

      And even if you disagree with me on those issues: If we have at most 10 or 20 years to head off catastrophic climate change, does it make any sense to focus our efforts on population programs that even the most optimistic populationists say will take 50 years to have a marginal effect?