Second, I’m still skeptical that the historical war data is the “right” prior to use. It may be “a” prior but your title might be overstating things. This is related to Aaron’s point you quote in footnote 9, about assuming wars are IID over time. I think maybe we can assume they’re I (independent), but not that they’re ID (identically distributed) over time.
Historical war deaths seem to me like the most natural prior to assess future war deaths. I guess you consider it a decent prior too, as you relied on historical war data to get your extinction risk, but maybe you have a better reference class in mind?
Aron’s point about annual war deaths not being IID over time does not have a clear impact on my estimate for the annual extinction risk. If one thinks war deaths have been decreasing/increasing, then one should update towards a lower/higher extinction risk. However:
There is not an obvious trend in the past 600 years (see last graph in the post).
My impression is that there is lots of debate in the literature, and that the honest conclusion is that we do not have enough data to establish a clear trend.
I think Aron’s paper (Clauset 2018) agrees with the above:
Since 1945, there have been relatively few large interstate wars, especially compared to the preceding 30 years, which included both World Wars. This pattern, sometimes called the long peace, is highly controversial. Does it represent an enduring trend caused by a genuine change in the underlying conflict-generating processes? Or is it consistent with a highly variable but otherwise stable system of conflict? Using the empirical distributions of interstate war sizes and onset times from 1823 to 2003, we parameterize stationary models of conflict generation that can distinguish trends from statistical fluctuations in the statistics of war. These models indicate that both the long peace and the period of great violence that preceded it are not statistically uncommon patterns in realistic but stationary conflict time series.
I think there is also another point Aron was referring to in footnote 9 (emphasis mine):
you have a deeper assumption that is quite questionable, which is whether events are plausibly iid [independent and identically distributed] over such a long time scale. This is where the deep theoretical understanding from the literature on war is useful, and in my 2018 paper [Clauset 2018], my Discussion section delves into the implications of that understanding for making such long term and large-size extrapolations.
Relevant context for what I highlighted above:
Clauset 2018 did estimate a 50 % probability of a war causing 1 billion battle deaths[15] in the next 1,339 years (see “The long view”), which is close to my pessimistic scenario [see post for explanation]
I think Aron had the above in mind, and therefore was worried about assuming wars are IID over a long time, because this affects how much time it would take in expectation for a war to cause extinction. However, in my post I am estimating this time, but rather the nearterm annual probability of a war causing extinction, which does not rely on assumptions about whether wars will be IID over a long time horizon. I alluded to this in footnote 9:
Assuming wars are IID over a long time scale would be problematic if one wanted to estimate the time until a war caused human extinction, but I do not think it is an issue to estimate the nearterm annual extinction risk.
It is possible you missed this part, because it was not in the early versions of the draft.
I think we can be pretty confident that WWII was so much larger than other wars not just randomly, but in fact because globalization[1] and new technologies like machine guns and bombs shifted the distribution of potential war outcomes.
Some thoughts on the above:
What directy matters to assess the annual probability of a war causing human extinction is not war deaths, but annual war deaths as a fraction of the global population. For instance, one can have increasing war deaths with constant annual probability of a war causing human extinction if wars become increasinly long and population increases. Hopefully not, but it is possible wars in the far future will routinely wipe out e.g. trillions of digital minds while not posing any meaningful risk of wiping out all digital minds due to the existence of a huge population.
It is unclear to me whether globalisation makes wars larger. For example, globalisation is associated with an expansion of international trade, and this can explain the “durable peace hypothesis” (see Jackson 2015).
In agreement with deterrence theory, I believe greater potential to cause damage may result in less expected damage, although I am personally not convinced of this.
Even if globalisation makes wars larger, it could make them less frequent too, such that the expected annual damage decreases, and so does the annual probability of one causing extinction.
And I think similarly that distribution has shifted again since. Cf. my discussion of war-making capacity here. Obviously past war size isn’t completely irrelevant to the potential size of current wars, but I do think not adjusting for this shift at all likely biases your estimate down.
I assume increasing capability to cause damage is the main reason for people arguing that future wars would belong to a different category. Yet:
I think war capabilities have been decreasing or not changing much in the last few decades:
“Nuclear risk has been decreasing. The estimated destroyable area by nuclear weapons deliverable in a first strike has decreased 89.2 % (= 1 − 65.2/601) since its peak in 1962” (see 1st graph below).
Military expenditure as a fraction of global GDP has decreased from 1960 to 2000, and been fairly constant since then (see 2nd graph below).
Taking a broader view, war capabilities do have been increasing, but there is not a clear trend in the deaths in conflicts as a fraction of the global population since 1400 (see last figure in the post).
Increases in the capability to cause damage are usually associated with increases in the capability to prevent damage, which I guess explains what I said just above, so one should not forecast future risk based on just one side alone.
Historical war deaths seem to me like the most natural prior to assess future war deaths. I guess you consider it a decent prior too, as you relied on historical war data to get your extinction risk, but maybe you have a better reference class in mind?
Aron’s point about annual war deaths not being IID over time does not have a clear impact on my estimate for the annual extinction risk. If one thinks war deaths have been decreasing/increasing, then one should update towards a lower/higher extinction risk. However:
There is not an obvious trend in the past 600 years (see last graph in the post).
My impression is that there is lots of debate in the literature, and that the honest conclusion is that we do not have enough data to establish a clear trend.
I think Aron’s paper (Clauset 2018) agrees with the above:
I think there is also another point Aron was referring to in footnote 9 (emphasis mine):
Relevant context for what I highlighted above:
I think Aron had the above in mind, and therefore was worried about assuming wars are IID over a long time, because this affects how much time it would take in expectation for a war to cause extinction. However, in my post I am estimating this time, but rather the nearterm annual probability of a war causing extinction, which does not rely on assumptions about whether wars will be IID over a long time horizon. I alluded to this in footnote 9:
It is possible you missed this part, because it was not in the early versions of the draft.
Some thoughts on the above:
What directy matters to assess the annual probability of a war causing human extinction is not war deaths, but annual war deaths as a fraction of the global population. For instance, one can have increasing war deaths with constant annual probability of a war causing human extinction if wars become increasinly long and population increases. Hopefully not, but it is possible wars in the far future will routinely wipe out e.g. trillions of digital minds while not posing any meaningful risk of wiping out all digital minds due to the existence of a huge population.
It is unclear to me whether globalisation makes wars larger. For example, globalisation is associated with an expansion of international trade, and this can explain the “durable peace hypothesis” (see Jackson 2015).
In agreement with deterrence theory, I believe greater potential to cause damage may result in less expected damage, although I am personally not convinced of this.
Even if globalisation makes wars larger, it could make them less frequent too, such that the expected annual damage decreases, and so does the annual probability of one causing extinction.
Related to the above, I commented that: