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I'm not a mathematician, but I'm trying to wrap my head around this statistical problem ...

An Oxford 2008 study guessed the likelihood of global extinction at 0.2%pa, which by my calculation is roughly 20% in the next 100 years, no? The Stern review reckons half that. But either way this is total extinction, not simply a catastrophe, which is what I'm trying to quantify here. This report defines a global catastrophe as 10% of the world dying, which is 2-4x worse than the worst thing that happened last century (spanish flu), but good enough as a benchmark if that's what the experts are focussing on.

Now, my questions are:

  1. If it's 0.2% likely that we'll lose 100% of our population in the next year, then is it correct to calculate the likelihood of losing 10% of our population in the next year to be 10x as likely, or 2.0%?

  2. How can I extrapolate that out to the likelihood of it happening in my lifetime, say, the next 40 years? Is it as simple as just multiplying it by 40, making it 80%?

Reference Article (page 24)

kjetil b halvorsen
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harvest316
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    You should understand the underlying logic to derive the 0.2%. They may talk about the extreme event lying in the fat tail. You cannot simply do the extrapolation as any distribution is highly non-linear. – hbadger19042 Jun 06 '20 at 02:30
  • Thanks Kevin. This is a good question which is rather beyond me. But I can tell you than its an aggregate of a range of very different risks (eg: pandemic, asteroids, climate change, etc) each of which were calculated differently. – harvest316 Jun 06 '20 at 05:31

1 Answers1

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Check the reference for the figure mentioned by the report:

Sandberg, A. & Bostrom, N. (2008): “Global Catastrophic Risks Survey”, Technical. Report #2008-1, Future of Humanity Institute, Oxford University: pp. 1-5.

It explains where does the number comes from and what it means:

At the Global Catastrophic Risk Conference in Oxford (17‐20 July, 2008) an informal survey was circulated among participants, asking them to make their best guess at the chance that there will be disasters of different types before 2100. This report summarizes the main results.

On the first page it mentions the number for "Overall risk of extinction prior to 2100" to be 20%. First, notice that this is just a survey, so subjective opinions of people. Second, the question asked the participants to guess the number for the period till the year 2100. I don't think you can use this number to interpolate or extrapolate. For example, if we consider risk due to something like climate changes, this risk would probably grow incrementally in an exponential fashion, so it would be low in the next few years, but then start rapidly growing--so it would not grow linearly. Third, humans perceive numbers, and probabilities in particular, on subjective scales, that not necessarily correspond to their actual "raw" numeric values. I wouldn't do math on guessed numbers.

Tim
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