Financial returns of interstellar colonization for the sedentary

Summary: In thinking about the likelihood of interstellar colonization by our civilization, or possible alien civilizations, one question is motivation: how strong are the incentives to do so? If moderately fast self-replicating probes can build infrastructure in a new solar system and send back information or material goods requiring extensive experimentation or computation to produce, then even at current market interest rates a colonization mission could deliver extremely high return on investment. For patient long-lived decision-makers with strong property rights or stability, returns could be overwhelming.

Flow-through effects of innovation through the ages

Summary: Per the previous post, it appears that growth impacts of saving lives have historically dwarfed the immediate effects, by increasing technological innovation that eventually led to the rich and populous modern world. Active work on technological innovation contributes more to technology than the average of all activity in society, and so might be expected to have larger growth effects. Moreover, in ancient times not only did society have smaller population and output, it also invested much less of those resources into R&D. The greater neglectedness raised the marginal impact of ancient R&D enormously, so that past altruists who contributed to innovation could have had multiple orders of magnitude more impact on long-run living standards and years of life lived than those who saved lives or provided direct aid. The strength of this preference increases enormously as we consider earlier periods in history.

Flow-through effects of saving a life through the ages on life-years lived

Summary: Historically, human populations were much smaller, and humans have long contributed to a process of technological accumulation that lead to current enormous human populations. Thus, saving a drowning child 10,000 years ago would have, by increasing economic output and technological advance, lead to hundreds of additional human lives by today, and potentially far more in the future. Because past populations were smaller by a greater factor than they were poorer, the ancients' opportunities to bring about QALYs may be much greater and closer to those of moderns than is sometimes thought, at least within the field of local direct life-saving. Impacts were also enormously greater in comparatively non-Malthusian periods, when a saved life could compound at high local population growth rates. In some ways, this is a historical analog to Nick Bostrom's 'Astronomical Waste' argument, showing that the basic logic of longtermism has held in the past in at least some domains. However, expediting growth is a relatively easy change to transmit over long periods, whereas trajectory changes that attempt to shape the character or actions of society at future technology levels (rather than when they are reached) face the problem of decaying influence.

Philosophers vs economists on discounting

Temporal discounting is not about time
Economists doing cost-benefit analysis normally make use of temporal discounting, i.e. benefits further in the future count for less than those nearer to the present. In part this is done to reflect the availability of positive investment returns, but normally analysis also include an additional element of pure temporal preference.

Say that I set up a sealed habitat for some plants and cute bunny rabbits. The rabbits are placed in suspended animation, and the habitat is rocketed out of the Solar System by an automated spacecraft which will never return to interact with our world again. At a predesignated time, the rabbits will be revived and go on to live happy lives in the sealed habitat for a time and then die. With significant pure temporal preference this spacecraft is much more valuable if it is set to revive the isolated rabbits after 5 years rather than 50.

Indeed, economists typically make use of constant exponential discounting, e.g. reducing the valuation of benefits by 3% per year. At a 3% annual discount rate the value of future benefits will be cut by more than half every 23 years. After 230 years a good would be valued at less than a thousandth of an immediate counterpart.   But to most people the change in activation time does not make such an overwhelming difference. Further, constant exponential discounting makes strong distinctions between different far-future periods: benefits received in 1 million years are still more than a thousand times as valuable as benefits received in 1,000,230 years.

But real humans mostly don't care about such distinctions. A difference of a few centuries added onto a  million years is a negligible change in time: in either case they lie far beyond the current era and the proportional change is small. Favoring the earlier time for a thousandfold reduction in the goods achieved seems absurd in that context. Humans may be impatient within our own lives, care more about our children than distant descendants, and so forth, but the constant exponential discounting framework just doesn't make sense of our attitudes towards the further future.

Because of cases like this philosophers tend to reject the idea of pure temporal preference for social cost-benefit analysis, e.g. with respect to climate change, and often critique economists for persisting in making use of it. But economists are not fools, and the reasons why so many continue to do so are worth thinking about.