In talking with people about the long-term future, I've found it to be extremely helpful to give an estimate for the percent chance humanity goes extinct by 2100 (or in 100 years). Right now, I say ~10% or 5-19%, and then say something like "it would be really nice if we could get that number below 1%". My estimate is taken from these sources:

- FHI's casual 2008 survey of various x-risks. Taken together, they give a 19% chance by 2100.
- The 2007 Stern Review, a 700-page report on climate change. It uses 0.1% as an upper bound modeling assumption for annual extinction risk, which means 9.5% in the next 100 years (by 2107).
- This July 2018 Vox article from Liv Boeree that references the FHI study and also says "5 to 19 percent chance of complete human extinction by the end of this century". (I'm not sure where the 5% comes from?)
- This 2016 report on GCRs from FHI and the Global Priorities Project. They reference the two sources above and just say it's hard to create a reasonable estimate.

However, I find the strength of these estimates pretty weak. If someone were to ask me to "back up" my 10% number, the best I'd have is an informal survey circulated at an x-risk conference in 2008. So, a couple questions:

- Are there other sources that I'm missing?
- Do others also feel like it would be
*helpful*to have an updated/more rigorous estimate here? (Or is it not actually helpful to operate at this level of abstraction? i.e. Should we concentrate just on individual sources of x-risk instead?) - Is it even
*possible*to create an estimate like this? Or is the range of uncertainty just too large, that we'd need to give an estimate like 2-59%? (Clearly, this gets more difficult the longer we try to project out. But can't we estimate it for 2050, 2075, or 2100?)

Thanks for your thoughts and help!

Hey Simon! Thanks writing up this paper. The final 1/3 is exactly what I was looking for!

Could you give us a bit more texture on why you think it's "best not to put this kind of number on risks"?

Hey Rhys

Thanks for prompting me on this. I was hoping to find time for a fuller reply to your but this will have to do, you only asked for the texture after all. My concerns are somewhat nebulous so please don't take this as any cast iron reason not to seek out estimates for the probability of different existential risks. However, I think they are important.

The first relates to the degree of uncertainty that surrounds any estimate of this kind and how it should be handled. There are actually several sources of this.

The first of these relates to the thresho... (read more)