Re 3⁄3.1: When discussing the marginal returns on a human life, a quantitative way of modelling human capability could be as the product of sigmoidal curves with positive and negative slopes to represent the scaling up of capability during development and scaling down of capability during natural aging. As long as aging doesn’t kick in before development is finished then there is a plateau phase during which a person can perform at maximum capability and should produce constant returns on extra years in this phase.
Treating treating human capability as a single curve might be too simplistic. One could further break this down to intellectual and physical capability and intrinsic and extrinsic factors:
-Physical capability is simplest as humans probably reach peak intrinsic physical capability around 20 (sharp increase) and start to decline after 40 (slow decline). I’m not sure there are extrinsic factors related to physical capability that will change as a function of a person’s life span.
-Intrinsic intellectual capability could probably continue to scale up for a long time with a slow increase (some luminaries may currently get close to peak intellectual capacity, but I suspect that most people alive at the moment don’t) and this does not necessarily decline much during aging unless somebody gets an age related neurological disorder (which can cause a very sharp decline). While some might argue that people will keep increasing intellectual capability with age, I’d argue that there probably is an upper limit to intrinsic intellectual capability given the brain’s capacity to store and process information (although neurotechnology may extend this). However, extrinsic intellectual factors like professional network size, strength, and value generally do continue to increase over time and could be modelled as a curve with a slow increase; while social network size currently tends to decline in old age this seems to be related to declining physical capability (reduced stamina limiting ability to socialize and forcing retirement) and so improving physical health during old ago may also prevent decline in some extrinsic intelectual areas.
Productivity could then be judged as weighted sums and/or products of intrinsic and extrinsic intellectual and physical capability. The weighting will probably depend on the state of the society an individual lives and would change over time—subsistence farming would weight physical capability strongly, developed society initially favoured intrinsic intellectual capability but increased digital connectivity is increasing the value of extrinsic intellectual factors.
The reason I focus on a model composed of weighted sums/products of sigmoidal curves of positive/negative slopes is that these can actually create fairly interesting results. The sum or the product of two sigmoidal curves with opposing slopes will be something like a bell curve (although it can be flat topped and have asymmetric sides), which probably agrees quite well with how people would judge the productivity of a current human life-span. However, having three sigmoid curves with the result depending on the product of two of them can create a local maxima before a later plateau, which could be used to represent an early peak in productivity due to physical capacity that will later be exceeded by intellectual capability (see this figure for an example I used of such a model https://www.nature.com/articles/srep02614/figures/5 ). Also, sigmoidal curves are quite good at describing many biological processes.
In summary, the point I’m getting at is there could be a good biological/psychological framework to discount life years based on both development and aging.
*Note that I don’t have much experience in population ethics and am implicitly equating productivity to value and this may not be a good ethical framework (although I assume it will probably be agreeable to economists!).
Re 3.2: People also often do riskier things earlier in their lives. You don’t see many 50 year old startup founders, maybe because they a more likely to need guaranteed income to to support their kids and/or for retirement savings. But their greater knowledge and connections may give them a greater chance of success at high-risk/high-reward type endeavours, and so LEV may allow people to undertake such promising activities later in life when they are better prepared for them.
Re 3⁄3.1: When discussing the marginal returns on a human life, a quantitative way of modelling human capability could be as the product of sigmoidal curves with positive and negative slopes to represent the scaling up of capability during development and scaling down of capability during natural aging. As long as aging doesn’t kick in before development is finished then there is a plateau phase during which a person can perform at maximum capability and should produce constant returns on extra years in this phase.
Treating treating human capability as a single curve might be too simplistic. One could further break this down to intellectual and physical capability and intrinsic and extrinsic factors:
-Physical capability is simplest as humans probably reach peak intrinsic physical capability around 20 (sharp increase) and start to decline after 40 (slow decline). I’m not sure there are extrinsic factors related to physical capability that will change as a function of a person’s life span.
-Intrinsic intellectual capability could probably continue to scale up for a long time with a slow increase (some luminaries may currently get close to peak intellectual capacity, but I suspect that most people alive at the moment don’t) and this does not necessarily decline much during aging unless somebody gets an age related neurological disorder (which can cause a very sharp decline). While some might argue that people will keep increasing intellectual capability with age, I’d argue that there probably is an upper limit to intrinsic intellectual capability given the brain’s capacity to store and process information (although neurotechnology may extend this). However, extrinsic intellectual factors like professional network size, strength, and value generally do continue to increase over time and could be modelled as a curve with a slow increase; while social network size currently tends to decline in old age this seems to be related to declining physical capability (reduced stamina limiting ability to socialize and forcing retirement) and so improving physical health during old ago may also prevent decline in some extrinsic intelectual areas.
Productivity could then be judged as weighted sums and/or products of intrinsic and extrinsic intellectual and physical capability. The weighting will probably depend on the state of the society an individual lives and would change over time—subsistence farming would weight physical capability strongly, developed society initially favoured intrinsic intellectual capability but increased digital connectivity is increasing the value of extrinsic intellectual factors.
The reason I focus on a model composed of weighted sums/products of sigmoidal curves of positive/negative slopes is that these can actually create fairly interesting results. The sum or the product of two sigmoidal curves with opposing slopes will be something like a bell curve (although it can be flat topped and have asymmetric sides), which probably agrees quite well with how people would judge the productivity of a current human life-span. However, having three sigmoid curves with the result depending on the product of two of them can create a local maxima before a later plateau, which could be used to represent an early peak in productivity due to physical capacity that will later be exceeded by intellectual capability (see this figure for an example I used of such a model https://www.nature.com/articles/srep02614/figures/5 ). Also, sigmoidal curves are quite good at describing many biological processes.
In summary, the point I’m getting at is there could be a good biological/psychological framework to discount life years based on both development and aging.
*Note that I don’t have much experience in population ethics and am implicitly equating productivity to value and this may not be a good ethical framework (although I assume it will probably be agreeable to economists!).
Re 3.2: People also often do riskier things earlier in their lives. You don’t see many 50 year old startup founders, maybe because they a more likely to need guaranteed income to to support their kids and/or for retirement savings. But their greater knowledge and connections may give them a greater chance of success at high-risk/high-reward type endeavours, and so LEV may allow people to undertake such promising activities later in life when they are better prepared for them.