[Epistemic status: I am very confused, possibly about very basic Econ 101 things. Probably there is more research I could do to resolve my confusion but I don't have the time or motivation for that right now.]
[Update: Paul Christiano's comment resolved a reasonable part of my confusion, and gjm's comment seems to indicate this is probably the wrong discussion to be having.]
Recently there has been some discussion regarding the question of whether the fact that most people don't make long-term investments to help the future means that people don't care much about the future. To me this argument seems kind of silly: EAs have a hard enough time already getting people interested in ideas of how to help other people without one more weird idea in the mix. But I am more interested in the object-level question: is long-term investment actually a good way to help the future?
The basic argument in favor is simple. The power of compound interest means that if you invest, you will end up with more money (inflation-adjusted) than you started with, which in turn means that you can help more people. If we value all people equally, then this means a higher utility.
There are many possible objections but to me, the most obvious one is that it's not clear making $1000 by investing in the stock market means that you have added $1000 worth of value to the world, it could just mean that you have taken it from someone else. I do know enough Econ 101 to know the obvious counterargument: if you assume rational decision-making together with no negative externalities, then you have to have added $1000 worth of value to the world, because every deal that happens as a result of your investment was rationally consented to by the parties making the deal, and so can be assumed not to hurt them (according to the rationality assumption) nor anyone else (according to the assumption of no negative externalities). So everyone else is better off or at least not worse off than they were before, and you are $1000 better off. So $1000 of value has been added to the world. [Edit to clarify: The point of this argument is not supposed to be that the assumptions are always satisfied (they aren't), but that maybe they are satisfied often enough that we can expect a generic investment that makes $1000 to have added close to $1000 of real value to the world.]
Those seem like pretty strong assumptions to me though, and the conclusion seems pretty weird if you think about it. Namely, you are saying that just by making some trades that at the time don't make anyone better off or worse off, you end up creating something of real value. But the trade itself clearly isn't what's creating the real value, so it must be being created in some hidden way. What is the causal mechanism linking the trade to the creation of value? I can't see it.
As an example, suppose someone sells you a stock, which you intend to keep for a long time, whereas otherwise you would have just kept the money for a long time. If we assume that the person you are buying the stock was also going to hold on to it, and will hold onto the money as well, then the trade actually does not create value. Now this scenario contradicts the rational decision-making assumption because if the other guy is just going to keep the money, then it would be better for him not to sell the stock. So he is going to spend it instead, and that will cause some sort of ripple effects throughout the economy. Somewhere in these ripple effects, it seems, we are to believe that the real value is created. But the longer the ripple, it seems, the more chance there is for irrational action, so that in the end maybe you are just taking money from someone stupid. How can we estimate the chance of this versus the chance that the ripple effect will cause real value?
Here is another way that I tried to wrap my mind around it. Consider a simplified model where everyone has to choose whether to consume resources or create resources. Then maybe by doing this trade, you are moving the incentive structure in the direction of incentivizing resource creation. People "could have" created resources anyway, but they didn't want to. So in the end you are basically paying people to create resources, which is an action that doesn't help them but helps the future. But its effect on them is essentially the same as if you had paid them to do something else.
So, am I thinking about this the right way? Is there any good way to empirically estimate how much value is created by an investment? Or am I concentrating on the wrong objection and other objections are actually more important? (Another possible objection is that maybe mitigating X-risk now is more important, or equivalently maybe our ability to use resources to mitigate X-risk is decreasing at a rate comparable or faster to the growth rate of investments. How fast is our ability to mitigate X-risk decreasing? Is it decreasing?)
(Note: The comment threads of the two posts I linked to in the first paragraph contain some valuable discussion I won't reproduce here; so does the comment thread of this old post. Also, this post summarizes some discussion on the related question of whether short-term investment (by which I mean years or decades rather than centuries or millenia) is worthwhile from an EA perspective.)
Curiously, from a civilisational perspective it doesn't matter whether you invest the money or just stuff it in your mattress; either way you're creating capital relative to the alternative, which is to spend it now on some form of consumption. (Note that, in this view, charitable giving is a consumption good rather than a capital good. In practice, of course, it's more complicated, because Africans with mosquito nets are more likely to generate endogenous economic growth than Africans with malaria. But to first order, saving African lives is that-which-you-value, rather than a means of producing more of that-which-you-value; ergo, it's a consumption good.)
The key idea I think you might be missing is that capital is deferred consumption. That is, whenever we postpone our consumption from time X to time Y, we create capital that exists for the interval [X, Y). If we invest the money, this is obvious: the factory built with our investment is a capital good, and the profit we make depends on the stuff the factory makes being worth more than was invested to build it.
But suppose instead of investing the money, we just bury it for ten years. During those ten years, there is less money in circulation than otherwise, which drives up the value of money. I.e., it drives down the prices of goods. This means that all other holders of money now have access to slightly more capital, and can fund larger investments with the same number of banknotes. The capital is still created, and still produces a dividend, it's just that that dividend is now paid to people who are actively investing, instead of to us.
How can this be? Well, how did we earn the money in the first place? We produced some good or performed some service, and in return received only these green pieces of paper. If we just sit on them, they are sterile to us; but we still performed the service. Essentially, we are only paid for our work when we spend our wages on consumption goods (or services); it is in those goods that we are really paid. So burying our money for ten years is waiting ten years to present our claim upon society to be rewarded for the work we previously furnished. If that work was to build someone a factory, then for those ten years the factory is producing goods for a society that hasn't paid for the factory yet; if that work was to supply someone with consumption goods, then just follow the chain of substitutions / opportunity costs until you get to a capital good.
Of course, for this to work, someone has to be investing in actual capital goods; and the more people are doing so independently, the more loci of initiative are searching for profitable opportunities (and the fewer possibly-irrational trades you have to follow before hitting a capital good). So investing the money does slightly improve the system's efficiency at finding and making the best available investments. But it's the earning the money, not the investing it, that creates the value which, by deferral of consumption, becomes capital. (Thus, investing unearned income / ill-gotten gains does not create capital!)
When I wrote about trades not creating real value, I just meant that any value created in the trade is incidental and not the main thing we are talking about. Like, economic theory says we should expect $1000 of value to have been created even if our trade didn't create any value (perhaps because both buyer and seller were indifferent to whether or not to trade). Of course I understand the point about moving existing stuff to higher-valued uses.
The idea that burying money is as good as investing it seems to contradict Paul Christiano's explanatio... (read more)