FOR no particular reason, every time I sit down with an economist today, the Stern Report on global warming comes up.  I am not speaking to environmental economists, nor do I bring the topic up to anyone.  Yet each time, it somehow worms its way into the conversation.

Those following the conversation at home will perhaps remember that the Stern report was undertaken at the behest of the British government, in an attempt to find out how much global warming was going to cost in the future, and what we should be prepared to do about it now.  It became controversial among economists because of Sir Nicholas Stern's decision to choose a pure time discount rate of zero for the future benefits of climate change abatement.  In everyday language, that means that when weighing costs and benefits accruing to those of us alive now, against the costs and benefits to future generations, we get no "extra credit" for being alive closer to this year.  A 1% decrease in income today is treated as the exact equivalent of a 1% decrease in income 200 years from today.  William Nordhaus has been among the chief critics of this approach.

I am still chewing over the full import of the moral intuition that people born 100 years from now have just as much right to, say, live in Bangladesh, as those born today. But as one does, when one is chatting with economists, I became curious about what this moral intuition would mean if we actually applied it.  The most obvious example is abortion.  If we cannot discount the interests of the fetus simply because it is not yet with us as a person, then how can one morally justify legal abortion as a coherent national policy?  In the United States, at least, the argument generally centres around whether or not the fetus is a "person"—an argument which only makes sense, given the time horizon, with a very aggressive use of time preference.  I found myself becoming very curious whether economists who support Sir Nicholas's pure time discount rate of near zero, such as econ bloggers John Quiggin and Brad DeLong, identify themselves as pro-choice or pro-life, and whether they had considered the Stern Report from this angle. 

Then I began exploring the permutations that might logically reconcile favouring legal abortion, on the one hand, and perfect concern for the welfare of unnamed descendants 2,000 years hence.  Is it that the unnamed descendants are not yet fetuses?  Does non-fetushood convey protections?  But surely, barring scientific advance, they will eventually be fetuses, before they are people. 

Is it that they aren't specific, but only general?  I cannot build any moral logic does not dictate that any preference should run the other way, in favour of creatures with a high genetic likelihood of existing in a particular form.  Besides, we know that environment strongly influences who we will eventually be, so we don't know exactly what person the fetus will become.  Therefore, I mote, the future he or she should be able to collect any considerations owed to the amorphous future over the specific.

{I think I need an entirely new tense to have this discussion.}

There are, of course, other arguments in favour of legalised abortion.  One could say, for example, that women have no obligation to support a fetus just because it happens to be helplessly dependant—but this would seem to undercut any moral support for the social safety net and the income tax.  Saying that bodies are different might make some sense, but personally, I take my body to work with me every day, after which the various levels of American government will take forty percent of the labour of my fingers, at gunpoint if necessary. 

I find it hard to construct a really compelling argument in favour of abortion which does not rest in some way on discounting the utility of the fetus-as-future-person.  Though I have not myself been pregnant, I observe that my friends and relatives appear to prefer the horrors of pregnancy to not being alive.  Thus, comparing straight utility, the fetus should win in a cost-benefit analysis.

Update:  Social discount rate has been clarified to pure time discount rate.