Yes, discount rates are an important thing to discuss here. I briefly discuss them on pp. 63-64 of my dissertation (http://www.nickbeckstead.com/research). I endorse using discount rates on a case-by-case basis as a convenience for calculation, but count harms and benefits as, in themselves and apart from their consequences, equally important whenever they occur.
For further articulation of similar perspectives I recommend:
Cowen, T. and Parfit, D. (1992). Justice Between Age Groups and Generations, chapter Against the Social Discount Rate, pages 144–161. Yale University Press, New Haven.
What do you mean by “using discount rates on a case-by-case basis as a convenience for calculation”?
I don’t find your dissertation discussion very convincing (but then I’m an economist). I worry a lot more about the existing real children with glass in their feet right now (or intestinal worms or malaria or malnutrition or whatever) than the hypothetical potential children of the future who don’t exist yet, and in any case when they do will live in a substantially wealthier society in which everyone has access to good quality footwear.
I like to distinguish between pure discounting and discounting as a computational convenience. By “pure discounting,” I mean caring less about the very same benefit, which you’ll get with certainty in the future, than a benefit you can get now. I see this as a values question, and my preference is to have a 0% pure discount rate. One might discount as a computational convenience to adjust for returns on investment from having benefits arrive earlier, uncertainty about the benefits arriving, changes in future wealth, or other reasons.
When you are deciding how to discount, I find it easiest to think about the problem without any discounting of any kind (doing something like a classical utilitarian analysis) and explicitly think about the empirical effects. Then if you want to use discounting as a computational convenience, you can try to choose one that gives similar results to thinking about the problem without any kind of discounting.
I might be able to respond better if you told me how you think an appropriate treatment of discounting might affect the conclusions that Carl and I drew.
I think your choice of discount rate is going to fundamentally alter your investment decision, it’s not just some kind of marginal technical tweak.
In practice either you discount fairly heavily, as most public projects do, and end up putting most of your money into solving short-term suffering (as I think you should), or you discount lightly, and put most of your money into possible future catastrophic risk mitigation.
I don’t see how this is “computational convenience”—it’s fundamental.
I agree that a choice of discount rate is fundamentally important in this context. If you did the standard thing of choosing a constant discount rate (e.g. 5%) and used that for all downstream benefits, even ones millions of years into the future, that would make helping future generations substantially less important. By emphasizing the distinction between pure discounting and discounting as a computational convenience, I did not mean to suggest that views about how to discount future benefits were unimportant.
I was distinguishing between two possible motives for discounting that I think clarifies what the purpose of discounting should be. The two purposes are hard to disentangle because they overlap in practice, but I think they diverge when it comes to distant future generations. I can try to explain more if you haven’t understood what the distinction I’m intending is. It’s the difference between “Benefits now are better just because that’s what people prefer” and “benefits now are better because they cause compounding growth, future people will be richer, the future is uncertain, etc”. If you go for the second answer, the conclusion isn’t something like “use a 5% discount rate for all benefits, even ones a million years out”, but instead “use a discount rate that accurately reflects your beliefs about growth, uncertainty, marginal value of consumption, etc.” in the the distant future. For reasons I linked to in Hanson and Weitzman, that’s not what I expect. Briefly, constant exponential growth over million-year timescales is hard (but not impossible) to square with physics-imposed constraints on the resources we could have access to. And, as Weitzman argues, I believe uncertainty about future growth results in a form of discounting that looks more hyperbolic and less exponential in the long run. These differences are not very consequential over the next 50 years or something, but I believe they are very consequential when you consider the entire possible future of our species.
That last sentence would take more explaining than I have done in any work I’ve publicly written up, and it’s something I would like to get to in the future. I haven’t run into many people for whom this was the major sticking point for whether they accept the long-run perspective I defend. But if this is your sticking point and you think it would be for many economists, do let me know and I’ll consider prioritizing a better explanation.
Let me explain my position—first, I agree with rejecting a pure time preference, and instead doing discounting based primarily on expected growth in incomes.
For me, the expectation that in 50 years the average person could easily be twice as wealthy, leads to quite heavy discounting of investment to improve their welfare vs spending to alleviate suffering from extreme poverty right now.
It’s possible I haven’t thought this through thoroughly, and am explaining away my lack of enthusiasm for your choice of 5 causes to the neglect of the classic Givewell/GWWC choices. Perhaps there is something to do with efficacy there—that I’m unsure of the likely impact of funding immigration advocacy, forecasting, and more research.
Interesting stuff, but disappointed you don’t talk about discount rates.
Yes, discount rates are an important thing to discuss here. I briefly discuss them on pp. 63-64 of my dissertation (http://www.nickbeckstead.com/research). I endorse using discount rates on a case-by-case basis as a convenience for calculation, but count harms and benefits as, in themselves and apart from their consequences, equally important whenever they occur.
For further articulation of similar perspectives I recommend:
Cowen, T. and Parfit, D. (1992). Justice Between Age Groups and Generations, chapter Against the Social Discount Rate, pages 144–161. Yale University Press, New Haven.
and
http://rationalaltruist.com/2013/02/22/four-flavors-of-time-discounting-i-endorse-and-one-i-do-not/
What do you mean by “using discount rates on a case-by-case basis as a convenience for calculation”?
I don’t find your dissertation discussion very convincing (but then I’m an economist). I worry a lot more about the existing real children with glass in their feet right now (or intestinal worms or malaria or malnutrition or whatever) than the hypothetical potential children of the future who don’t exist yet, and in any case when they do will live in a substantially wealthier society in which everyone has access to good quality footwear.
I like to distinguish between pure discounting and discounting as a computational convenience. By “pure discounting,” I mean caring less about the very same benefit, which you’ll get with certainty in the future, than a benefit you can get now. I see this as a values question, and my preference is to have a 0% pure discount rate. One might discount as a computational convenience to adjust for returns on investment from having benefits arrive earlier, uncertainty about the benefits arriving, changes in future wealth, or other reasons.
When you are deciding how to discount, I find it easiest to think about the problem without any discounting of any kind (doing something like a classical utilitarian analysis) and explicitly think about the empirical effects. Then if you want to use discounting as a computational convenience, you can try to choose one that gives similar results to thinking about the problem without any kind of discounting.
Regarding the hypothetical richer kids vs. current kids, I agree that one should make adjustments for uncertainty about whether there will be future kids, diminishing marginal utility of consumption, and beliefs about future growth. I don’t think this is well-captured by a constant exponential discount rate into the distant future. There are a lot of reasons I think this. Two I can quickly link to are here (http://www.overcomingbias.com/2009/09/limits-to-growth.html) and here (http://www.sciencedirect.com/science/article/pii/S009506969891052X).
I might be able to respond better if you told me how you think an appropriate treatment of discounting might affect the conclusions that Carl and I drew.
I think your choice of discount rate is going to fundamentally alter your investment decision, it’s not just some kind of marginal technical tweak.
In practice either you discount fairly heavily, as most public projects do, and end up putting most of your money into solving short-term suffering (as I think you should), or you discount lightly, and put most of your money into possible future catastrophic risk mitigation.
I don’t see how this is “computational convenience”—it’s fundamental.
I agree that a choice of discount rate is fundamentally important in this context. If you did the standard thing of choosing a constant discount rate (e.g. 5%) and used that for all downstream benefits, even ones millions of years into the future, that would make helping future generations substantially less important. By emphasizing the distinction between pure discounting and discounting as a computational convenience, I did not mean to suggest that views about how to discount future benefits were unimportant.
I was distinguishing between two possible motives for discounting that I think clarifies what the purpose of discounting should be. The two purposes are hard to disentangle because they overlap in practice, but I think they diverge when it comes to distant future generations. I can try to explain more if you haven’t understood what the distinction I’m intending is. It’s the difference between “Benefits now are better just because that’s what people prefer” and “benefits now are better because they cause compounding growth, future people will be richer, the future is uncertain, etc”. If you go for the second answer, the conclusion isn’t something like “use a 5% discount rate for all benefits, even ones a million years out”, but instead “use a discount rate that accurately reflects your beliefs about growth, uncertainty, marginal value of consumption, etc.” in the the distant future. For reasons I linked to in Hanson and Weitzman, that’s not what I expect. Briefly, constant exponential growth over million-year timescales is hard (but not impossible) to square with physics-imposed constraints on the resources we could have access to. And, as Weitzman argues, I believe uncertainty about future growth results in a form of discounting that looks more hyperbolic and less exponential in the long run. These differences are not very consequential over the next 50 years or something, but I believe they are very consequential when you consider the entire possible future of our species.
That last sentence would take more explaining than I have done in any work I’ve publicly written up, and it’s something I would like to get to in the future. I haven’t run into many people for whom this was the major sticking point for whether they accept the long-run perspective I defend. But if this is your sticking point and you think it would be for many economists, do let me know and I’ll consider prioritizing a better explanation.
Let me explain my position—first, I agree with rejecting a pure time preference, and instead doing discounting based primarily on expected growth in incomes.
For me, the expectation that in 50 years the average person could easily be twice as wealthy, leads to quite heavy discounting of investment to improve their welfare vs spending to alleviate suffering from extreme poverty right now.
It’s possible I haven’t thought this through thoroughly, and am explaining away my lack of enthusiasm for your choice of 5 causes to the neglect of the classic Givewell/GWWC choices. Perhaps there is something to do with efficacy there—that I’m unsure of the likely impact of funding immigration advocacy, forecasting, and more research.