There are some contexts in which the difference between 99.999% and 99.9% is about the same as the difference between 10% and 90%.
It’s not 99.9% in the IPCC report.
Events that happen with 0.005 probability are worth planning for when they have high impacts. We care about asteroid defense when that probability is much lower.
Humanity has a good chance of getting destroyed in this century if decision makers treat 0.001 the same way as 0.0000000001.
The outside view suggests to me that much of the time experts are horribly overconfident, and some of the time they are distinctly underconfident (at least in what they say)
In what examples are are experts underconfident when they give 0.9 or 0.95 probabilities of an event happening.
I wasn’t trying to suggest it was; my apologies for (evidently) being insufficiently clear.
Events that happen with 0.005 probability are worth planning for when they have high impacts.
Yup, strongly agreed. But here the low-probability events we’re talking about here are things like “it turns out global warming wasn’t a big deal after all”. It would be sad to have spent a lot of money trying to reduce carbon dioxide emissions in that case, but it wouldn’t be much like (e.g.) being hit by an asteroid.
In what examples are experts underconfident when they give 0.9 or 0.95 probabilities of an event happening
I don’t have examples to hand, I’m afraid (other than the IPCC example we’re discussing here, though actually all we know there is that their probability estimate is somewhere between 0.95 and 1, and is probably below 0.99 since they didn’t choose to say “virtually certain”. (Only “probably” because when they list what the terms mean they say 95-100% and not 95-99% for “extremely likely”, and the best explanation I can see for that is that they are reserving the right to say “extremely likely” rather than “virtually certain” sometimes even though they think the actual probability is over 99%. This is one reason why I suspect them of understating their certainty on purpose: they seem to have gone out of their way to provide themselves with a way to do that.)
It’s not 99.9% in the IPCC report.
Events that happen with 0.005 probability are worth planning for when they have high impacts. We care about asteroid defense when that probability is much lower.
Humanity has a good chance of getting destroyed in this century if decision makers treat 0.001 the same way as 0.0000000001.
In what examples are are experts underconfident when they give 0.9 or 0.95 probabilities of an event happening.
I wasn’t trying to suggest it was; my apologies for (evidently) being insufficiently clear.
Yup, strongly agreed. But here the low-probability events we’re talking about here are things like “it turns out global warming wasn’t a big deal after all”. It would be sad to have spent a lot of money trying to reduce carbon dioxide emissions in that case, but it wouldn’t be much like (e.g.) being hit by an asteroid.
I don’t have examples to hand, I’m afraid (other than the IPCC example we’re discussing here, though actually all we know there is that their probability estimate is somewhere between 0.95 and 1, and is probably below 0.99 since they didn’t choose to say “virtually certain”. (Only “probably” because when they list what the terms mean they say 95-100% and not 95-99% for “extremely likely”, and the best explanation I can see for that is that they are reserving the right to say “extremely likely” rather than “virtually certain” sometimes even though they think the actual probability is over 99%. This is one reason why I suspect them of understating their certainty on purpose: they seem to have gone out of their way to provide themselves with a way to do that.)