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From Forbes in 2011:

In society after society, [Bill Gates] saw, when the mortality rate falls—specifically, below 10 deaths per 1,000 people—the birth rate follows, and population growth stabilizes.

Does population growth stabilize when the mortality rate falls below 10 deaths per 1,000 people?

What are the societies mentioned as "society after society?"

I know that "More economically developed countries...have lower fertility rates [BBC]." However, this doesn't specifically relate to a mortality rate below 10 deaths per 1,000 people. Where did the number of "10 deaths per 1,000 people" come from?

Note: @plasticinsect correctly pointed out "10 deaths per 1000 people over what period of time? Per year? Per month? Per day?" Forbes didn't address this, so your answer should.

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    10 deaths per 1000 people over what period of time? Per year? Per month? Per day? – plasticinsect May 1 at 17:36
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    @plasticinsect This is a good question, and certainly one I didn't address. I left it to your interpretation as that's exactly what the Forbes article did. In an answer, it would be great to support the period of time you have chosen, and even better to evaluate the other periods of time you have suggested. – Barry Harrison May 1 at 18:47
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    @plasticinsect: probably per year given the usual measure: en.wikipedia.org/wiki/… – Fizz May 5 at 1:01
  • After reading the article, and now that I've read up a bit on various mortality statistics, my best guess is that he probably meant the under-5 mortality rate: the number of deaths of children under 5 years old per 1000 live births. I say that because the numbers actually fit, and because it makes sense that low child mortality would correlate to lower birth rate. It's still just a guess though. – plasticinsect May 5 at 1:55
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    The problem for almost all generalisations on the pattern of population growth is that population is a dynamic system where the long term consequences take a long time to become apparent. Even if birth rates drop below the sustainable level (~2.2 children per woman) the population will keep growing for perhaps 30 years. So any theory has to specify when its prediction will become apparent. This greatly complicates judging any claim. – matt_black May 6 at 12:24
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This is obviously untrue at a a global scale assuming the usual measure of crude death rates per year, which around 8 deaths per 1,000 people per year. The world population keeps rising for now despite that.

Gates also doesn't specify a bound for the lag in his implication, e.g. 100 years or just a few years lag between cause and effect? Claims this vague they can be proven true by stretching them enough. The rate of growth of the world population is decreasing, so given enough (lag) time Gate's "prediction" might prove "true".

Generally speaking, lower mortality is associated with higher GDP per capita (see first link), which in turn is associated with lower natality. Some researchers even dispute the latter, finding a J-shaped curve if the Human Development Index is substituted for GDP/capita. (There's a temporal counterpart to that. The number of countries with a fertility rate below 1.3 had peaked in 2003 [over 20 countries], but that number was only around 5 in 2008.)

Without any numerical landmarks, what Gates is talking about is called the Demographic Transition Theory, and goes back 50-70 years:

The mainstream arguments of the theory are that fertility is high in poor, traditional societies because of high mortality, the lack of opportunities for individual advancement, and the economic value of children. All these things change with modernization or urban industrialism, and individuals, once their viewpoints become reoriented to the changes that have taken place, can make use of the new opportunities.

Wikipedia also has a rather verbose page on it.

In general researchers who have tried to quantify this theory and use it for predictions have been proven pretty wrong.

Though he was by no means the first to state the essentials of the theory of the demographic transition, Notestein early formulation is conventionally accepted as classic. [...] Notestein thought that the populations of Western and Central Europe would peak in about 1950 and decline thereafter. The corresponding date for Southern Europe was 1970. Like Thompson, Notestein assumed that fertility would fall more steeply than it did in fact. His estimate of the total world population in the year 2000 was 3.3 billion in contrast to today's [1996] expected figure of nearly six billion.

[...]

Even with the hindsight of 50 years it has not been resolved whether the demographic transition is a theory, a generalization, a framework for analysis or merely an 'idea'. Or is it an 'historical model, predictive model, or a mere descriptivte term'? The debate about thes status of transition theory continues to occupy a central place in demography.

In any case, there's no claim here (of Gates) precise enough to investigate further.

  • Thanks for answering! Have an upvote. I wouldn't be too quick to discount the possibility of this being true in some countries. I feel this is what Gates is alluding to. Of course, I'm not him and can't know what he is thinking. Question inspired by this TED talk. – Barry Harrison May 5 at 4:19
  • Forgot to mention: Timestamp 4:00, exact time ~4:15. – Barry Harrison May 5 at 4:49

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