I'm intrigued by this post at Free Exchange, a blog from the Economist, and the comment there.

The post mentions that the Stern Report on Global Warming uses a 0% discount for future human lives when calculating the costs and benefits of a particular action. Normally, an economist decides that when calculating benefits accruing in the future, a discount is used because of the uncertainty of the situation. It's possible that something unrelated will happen and the benefits will disappear, or the effect of our action will be different from what we expected.

However, this is kind of a moral dilemma for actions that would end up to be a close call. For example, should we ignore global warming now and cause huge costs to future generations, or should we sacrifice a huge amount of our current wealth/production capability, to make sure that those people don't have to pay the far higher costs?
Even if we need to pay half of what we produce every year to fix global warming forever, that cost is still far less than the price paid by our descendants if we do nothing. However, because we're the one paying the price, we dither about it.

I think that's not a good idea, and we should spend the money now to fix the problem for later. However, not enough people listen to me. It's not even that we'd have to spend all that much, really, if everyone made their efforts. And, the sooner we start, the less work we have to do, which will be spread out over a greater time span. Everything is better if we don't procrastinate (and please don't let my teachers ever hear that I said that)

But whatever. That's not really the point of the post over there, though it is interesting, and necessary background.

The point is that, if we refuse to discount the cost/benefits to future humans for global warming, we should do it for other social issues as well. Such as, the deficit. Cleaning up the Middle East and Africa. Solving AIDS (have I hit everything yet? No). And, abortion.

The minimum cost to the mother of carrying out the pregnancy is 9ish months of her life spent carrying a fetus in her belly, which is awkward, and probably costs more for food, plus a bit for lost work. Remember, the mother could always give up the child immediately after birth, so we shouldn't count costs of child rearing in this. The benefits of going through all this are those of being a mother, which is a questionable benefit (evidently) to some people. The cost of an abortion (at least early on) is pretty small, and the benefits are not having to go through with the pregnancy. However, if we include the costs and benefits that accrue to the potential human at a zero discount, they almost certainly outweigh the costs to the mother. Being alive, at any price, is better than not being alive.

So, I think I like this zero-discounting for human lives...and it should not be selectively enforced. However, I'm not sure if the guy who commented has a valid point or not. I think he's trying to worm his way out of the inevitable conclusion in terms of abortion, but he might be right about this individual case.

He says that using a 0% discount for a bunch of people is ok, but you can't use it to predict cost/benefits for individuals. In a general sense, it works, but individuals are too complicated to analyze like that, so we need to discount for probability, or even just use a different method to weigh our options.

I'm not sure this is valid. I think that the cost/benefits that we are doing (where alive = better than dead, either from and abortion or death caused by global warming) can be used in the case of individuals, so it works for this point. Does anyone agree with him, or understand him better than I do?

Update: There are now lots of comments. I'm talking about the one by pun.gent.