What makes the difference?
The difference is that one set of risks is insurable and the other is not.
An insurable risk is one which can be mitigated through diversification. You can insure your house against fire only because there are thousands of other people also insuring their houses against fire. One consequence is that insurance is cheaper than an individual guarantee: it would cost much more to make your specific house entirely fireproof.
The other difference (and that one goes against Cochrane) is that normal insurable risks are survivable (and so you can assign certain economic value / utility / etc. to outcomes) while existential risks are not -- the value/utility of the bad outcome is negative infinity.
The finance professor John Cochrane recently posted an interesting blog post. The piece is about existential risk in the context of global warming, but it is really a discussion of existential risk generally; many of his points are highly relevant to AI risk.
He also points out that the threat from global warming has a negative beta - i.e. higher future growth rates are likely to be associated with greater risk of global warming, but also the richer our descendants will be. This means both that they will be more able to cope with the threat, and that the damage is less important from a utilitarian point of view. Attempting to stop global warming therefore has positive beta, and therefore requires higher rates of return than simple time-discounting.
It strikes me that this argument applies equally to AI risk, as fruitful artificial intelligence research is likely to be associated with higher economic growth. Moreover:
So should we close down MIRI and invest the funds in an index tracker?
The full post can be found here.