Here’s a third resolution. Consider a utility function that is a weighted sum of:
how close a region’s population level is to the “ideal” population level for that region (i.e. not underpopulated or overpopulated)
average utility of individuals in this region (not observer-moments in this region)
AMF is replacing lots of lives that are short (therefore low-utility) with fewer lives that are long (therefore higher utility), without affecting population level much. The effect of this could be summarized as “35 DALYs”, as in “we increased the average lifespan by 35 DALYs / total population”.
(warning: made-up numbers follow). Suppose we make someone live for 40 years instead of 5 years by curing malaria. This reduces the fertility rate; let’s say one fewer 35-year life happens as a result. This has no effect on the average population level (part 1). We replaced a 5-year life plus a 35-year life with a 40-year life. If average lives in the region are 35 years long (and we’re pretending that life utility = length of life), then most of the effect on part 2 of the utility function comes from preventing a worse-than-average life from happening.
Suppose instead that we extend someone’s life from 40 years to 75 years (a gain of 35 DALYs). This reduces the fertility rate; let’s pretend that this prevents a 35-year life from happening. So we’re replacing a 40-year life plus a 35-year life with a 75-year life. From the perspective of part 2 of the utility function, this is exactly as good as curing a case of malaria. So it seems like you can measure life-extending measures in DALYs pretty naively and things work out (both 35-DALY improvements are equally good under the utility function).
Here’s a third resolution. Consider a utility function that is a weighted sum of:
how close a region’s population level is to the “ideal” population level for that region (i.e. not underpopulated or overpopulated)
average utility of individuals in this region (not observer-moments in this region)
AMF is replacing lots of lives that are short (therefore low-utility) with fewer lives that are long (therefore higher utility), without affecting population level much. The effect of this could be summarized as “35 DALYs”, as in “we increased the average lifespan by 35 DALYs / total population”.
(warning: made-up numbers follow). Suppose we make someone live for 40 years instead of 5 years by curing malaria. This reduces the fertility rate; let’s say one fewer 35-year life happens as a result. This has no effect on the average population level (part 1). We replaced a 5-year life plus a 35-year life with a 40-year life. If average lives in the region are 35 years long (and we’re pretending that life utility = length of life), then most of the effect on part 2 of the utility function comes from preventing a worse-than-average life from happening.
Suppose instead that we extend someone’s life from 40 years to 75 years (a gain of 35 DALYs). This reduces the fertility rate; let’s pretend that this prevents a 35-year life from happening. So we’re replacing a 40-year life plus a 35-year life with a 75-year life. From the perspective of part 2 of the utility function, this is exactly as good as curing a case of malaria. So it seems like you can measure life-extending measures in DALYs pretty naively and things work out (both 35-DALY improvements are equally good under the utility function).