RyanCarey comments on A Complete Quantitative Model for Cause Selection - Effective Altruism Forum

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Comment author: RyanCarey 20 May 2016 04:34:15AM *  1 point [-]

The constant (irreducible) extinction risk model is a good one, but here's the catch. You don't really know how low the irreducible risk is once all risk-reducing interventions are made. It could go down to 0.1% annually, (suppose there are some unavoidable sun flares or other cosmic disasters) or it could go down to near-enough to zero. We don't know which kind of world we'd end up in, but if you care a lot about the long-run future, it's the latter family of worlds that you're aiming to save, and on expected value, the notion of those first worlds (whose cosmic endowments are kinda doomed :p) don't really matter. So the point if that the constant irreducable extinction risk model is just good enough that it only needs a slight upgrade to get the right (opposite) answer!

Comment author: Carl_Shulman 20 May 2016 12:55:32PM 3 points [-]

With uncertainty about that extinction rate this Weitzman paper's argument is relevant:

A critical feature of the distant future is currently unresolvable uncertainty about what will then be the appropriate rate of return on capital to use for discounting. This paper shows that there is a well-defined sense in which the ‘‘lowest possible’’ interest rate should be used for discounting the far-distant future part of any investment project. Some implications are discussed for evaluating long-term environmental projects or activities, like measures to mitigate the possible effects of global climate change

Comment author: AGB 25 May 2016 07:32:39PM 1 point [-]

Why 'once all risk-reducing measures are made'? Presumably what we care about is the marginal risk-reduction measure we can make on the margin?

I see no reason to think returns here are close to linear, since a reduction in the extinction rate from 0.2% to 0.1% (500 years -> 1000 years) delivers half the benefits of going from 0.1% to 0.05% (1000 years -> 2000 years) which is half of the benefits of going from 0.05% to 0.025%, etc. So my very weak prior on 'marginal return on effort spent reducing extinction risk' would be that they would be roughly exponentially increasing with the overall magnitude of resources thrown at the problem.

Which means I don't think you can take the usual shortcut of saying 'if 10% of world resources were spent on this it would be a great return on investment, and diminishing returns, so me spending 0.00001% of the worlds resources is also a great return'.

With that said, massively increasing returns is extremely unusual and feels intuitively odd so I'm very open to alternative models; this came up recently at a London EA discussion as a major objection to some of the magnitudes thrown around in x-risk causes, but I still don't have a great sense of what alternative models might look like.

Comment author: RyanCarey 27 May 2016 04:53:22AM 0 points [-]

Yeah introducing diminishing returns into a model could change the impact by an order of magnitude but I'm trying to answer a more binary question: which

What I'm trying to look at is will an intervention to x-risk has a "long-run impact" e.g. either approx. the cosmic endowment or approx. the current milleneum. If you use a constant discount or an exponential discount, that's going to make all of the difference. And if you think there's some amount of existential risk that's irreducible, that forces you to include some exponential discounting. So it's kind-of different from where you're trying to lead things.