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The conventional wisdom of demographers is fundamentally flawed.

In the conversation "Why do so many think that population growth is an important issue for the environment? Don't they know the facts of demographics?" Hans Rosling uses the "facts" of demography to argue we don't have to worry about population growth. Demographers have fundamental flaws in their thinking. In short, they are dead wrong.

Consider a belief that has these 2 characteristics: 1) believers average more than 2 children, and 2) they successfully pass along that belief to the next generation to at an average of at least 2 of those children. This belief will overpopulate the planet. Imagine that 99% of the population are non-believers, and 1% are believers. It would take many generations for the believers to rise to sufficient numbers so that demographers would notice them, but in the end, the birth rate will be determined by the believers.

This logic shows us flaws in the data collection and interpretation techniques that demographers use. Demographers must prove that these belief characteristics cannot exist if there is any hope that the downward trend of birth rates will continue and stay at or below an average of 2 children.

Their sampling techniques filter out beliefs that are passed to the next generation. This error means that if demographers tried to find groups that have beliefs that are not behaving according to the demographic transition predictions, they won't find them in their data.

Demographers use extrapolation techniques to predict future birth rates, but the logic dictates that they must find groups that are averaging the most children, and monitor their growth.


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    May 2 2012: I don't really understand what John Taves is saying.

    Demographers not only rely on abstract projections. They rely on hard data. Every 10 years or so, states count their population. Recently they did a massive census in India. Most countries have decadal censuses. Compare these data every 10 years and you have a trend, on which you can base a projection. Demographers fine-tune their projections based on new data and trends. They've been doing this for decades.

    When it comes to the idea of the "99% non-believers and the 1% believers", I don't see the point either: if we go from 9.5 billion in say the year 2075 to 6 billion in the year 2150, and then "the believers" pop-up and add a billion people in the year 2200, - then what's the big deal? By then we'll have plenty of technologies to cope with 7 billion people.

    Demography is sound: look at data, then compare and project. But again, maybe I simply haven't understood what the author is trying to say.

    PS: by the way, the demographic transition is not a "belief", it's a social phenomenon that simply happens. As people get wealthier and migrate to cities, their fertility rate drops - universally, everywhere. It's not belief, it's the logic of social and economic relations.
    • May 7 2012: If I watch stars moving in the night, I can spot a trend and make a projection. The planet moves n degrees in m minutes. I can project the position of the stars and planets using this technique. The accuracy depends on the goal. If you want to use the stars for navigation, it stinks. If you want to know where to look for Jupiter in a few hours, it is fine. You can improve the projection by fine-tuning based on the new data and trends. Almost everyone will ignore the point about the required accuracy and tell you that this technique is junk. The logic of this topic shows us that the projection techniques demographers use for predicting birth rates, is junk.

      As evidenced by the following points, you've shown that at least for you, the demographic transition is a belief.

      1) You demonstrated, by using the concept I showed above, that the demographic transition theory cannot predict birth rates in 2200. Yet, you do not conclude it is junk.

      2) Stopping at the year 2200 and using 99% is not proof there is no problem. It illustrates nothing. The correct logic to project this to forever, and recognize that a belief with these two characteristics is morally wrong. (note: that "I have the right to have as many children as I want" is a belief that has these two conditions and it has near 0% non-believers).

      3) You assumed that we will have plenty of technologies to cope with 7 billion in 2200. This is not a logical assumption. Humans have discovered wind, water, coal, oil, uranium through history as cheaper and cheaper sources of energy. Most people make the mistake of projecting this sequence into the future. This is, to put it bluntly, an idiotic projection. Each time we discover an energy source, like say oil, there is one less energy source to discover. I am not saying that we will not be able to cope with 7 billion, but I certainly will not assume it. Oil runs out.

      Using the projection technique so badly is justifying a belief. This is not science.
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        May 9 2012: 1) That's an odd interpretation of what he said.

        2) It is in no way logical to attempt to project the hypothetical "to forever." It's almost like you want a demographer to look through some crystal ball.

        3) You made the claim "Demographers...are dead wrong." and have made other strong claims throughout the thread. And all this is based on a hypothetical situation which in turn is founded on the assumption of a belief that is on no way supported by observation in the real world. But when an opposing point is made, you point out assumptions and "certainly will not assume it", even though it is actually supported by the observation of what is an amazing rate of advancement over the past 100 years? That is, to put it bluntly, an obscene double standard.

        If you are referring to this thread, then I agree that this is not science.
        • May 9 2012: Re. #1, this is not specific so I cannot respond.

          Re. #2, by projecting this hypothetical forward we learn what we must not do. Humans must not have a belief with these characteristics. We also learn that a projection of future birth rates that does not factor in this concept is mathematically wrong. The last paragraph I wrote in the topic could be interpreted as a demand that demographers look through some crystal ball. I intended it to say that if demographers want to predict future birth rates they must deal with this concept.

          Re #3. The belief "I have the right to have as many children as I want" is nearly universal. It certainly satisfies the second condition; it is passed along to the next generation flawlessly. The set of humans that have this belief have never averaged less than 2, thus this belief satisfies both conditions. In short "no way supported by observation" is a bad observation. Before we observe data we must first observe logic.
        • May 9 2012: I do not see the double standard you are describing. You will need to point out any assumptions that I have made that are not logically correct. I have pointed out assumptions, and interpretations of observations, that do not make sense.

          I suspect you are misinterpreting the concept that this topic describes. It does not state that these beliefs do exist, however, the belief "I have the right to have as many children as I want" does have these 2 characteristics. It does not state that these beliefs will always exist, or must always exist. It makes no predictions of the future.

          Notice that the statement "a belief with these 2 characteristics will overpopulate the planet" does not predict the future. Similarly, "If I point this loaded gun at this child's head, and pull the trigger, the child will die" does not predict whether the gun will be fired, but the statement is totally accurate. The statement tells us what we must not do.

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