So, the $5,000 to save a human life actually saves more than one human life. The world fertility rate is currently 2.27 per woman, but expected to decline to 1.8 by 2050 and 1.6 by 2100. Lets assume this trend continues at a rate of −0.2 per 50 years until eventually it reaches zero at 2500. Since it takes two people to have children, we halve these numbers to get an estimate of how many human descendents to expect from a given saved human life each generation.
If each generation is ~25 years, then the numbers will follow a series like 1.135 + 0.9 + 0.85 + 0.8 … which works out to 9.685 human lives per $5000, or $516.26 per human life. Human life expectancy is increasing, but for simplicity lets assume 70 years per human life.
70 / $516.26 = 0.13559 human life years per dollar.
So, if we weigh chickens equally with humans, this favours the chickens still.
However, we can add the neuron count proxy to weigh these. Humans have approximately 86 trillion neurons, while chickens have 220 million. That’s a ratio of 390.
0.13559 x 390 = 52.88 human neuron weighted life years per dollar.
This is slightly more than 41 chicken life years per dollar. Which, given my many, many simplifying assumptions, would mean that global health is still (slightly) more cost effective.
You haven’t factored in the impact of saving a life on fertility. Check out this literature review which concludes the following (bold emphasis mine):
I think the best interpretation of the available evidence is that the impact of life-saving interventions on fertility and population growth varies by context, above all with total fertility, and is rarely greater than 1:1 [meaning that averting a death rarely causes a net drop in population]. In places where lifetime births/woman has been converging to 2 or lower, family size is largely a conscious choice, made with an ideal family size in mind, and achieved in part by access to modern contraception. In those contexts, saving one child’s life should lead parents to avert a birth they would otherwise have. The impact of mortality drops on fertility will be nearly 1:1, so population growth will hardly change.
Also you’re assuming neuron count should be used as proxies for moral weight but I’m highly skeptical that is fair (see this).
So, the $5,000 to save a human life actually saves more than one human life. The world fertility rate is currently 2.27 per woman, but expected to decline to 1.8 by 2050 and 1.6 by 2100. Lets assume this trend continues at a rate of −0.2 per 50 years until eventually it reaches zero at 2500. Since it takes two people to have children, we halve these numbers to get an estimate of how many human descendents to expect from a given saved human life each generation.
If each generation is ~25 years, then the numbers will follow a series like 1.135 + 0.9 + 0.85 + 0.8 … which works out to 9.685 human lives per $5000, or $516.26 per human life. Human life expectancy is increasing, but for simplicity lets assume 70 years per human life.
70 / $516.26 = 0.13559 human life years per dollar.
So, if we weigh chickens equally with humans, this favours the chickens still.
However, we can add the neuron count proxy to weigh these. Humans have approximately 86 trillion neurons, while chickens have 220 million. That’s a ratio of 390.
0.13559 x 390 = 52.88 human neuron weighted life years per dollar.
This is slightly more than 41 chicken life years per dollar. Which, given my many, many simplifying assumptions, would mean that global health is still (slightly) more cost effective.
You haven’t factored in the impact of saving a life on fertility. Check out this literature review which concludes the following (bold emphasis mine):
Also you’re assuming neuron count should be used as proxies for moral weight but I’m highly skeptical that is fair (see this).