There have been several posts recently about investing financially to give later. I am overall uncertain about whether the marginal donor should invest, but I worry that existing analyses are missing some key movement-building effects that might be important. In particular, it seems plausible to me that:

• Maximizing the fraction of the world’s population that’s aligned with longtermist values is comparably important to maximizing the fraction of the world’s wealth controlled by longtermists.
• A substantial fraction of the world population can become susceptible to longtermism only via slow diffusion from other longtermists, and cannot be converted through money.

If the above are true, we may want to invest only if we think our future money can be efficiently spent creating new longtermists. If we believe that spending can produce longtermists now, but won’t do so in the future, then we should instead be spending to produce more longtermists now instead.

Illustrative mathematical model

[Disclaimer: I am not an economist. Phil Trammell looked at this model and said that it does demonstrate my overall point, but also that the better way to do this would probably use control theory.]

[Update: Changes made after super helpful comment from Michael Dickens below.]

I created an extremely simplified model to try and illustrate the effects of spending on movement building vs. investing. In this model:

• Our goal is to maximize the number of longtermists at some critical time t (perhaps the hinge of history).
• We start with some number of longtermists and some number of people susceptible to longtermism.
• Each year, the number of susceptible people grows by some amount proportional to the number of longtermists that year.
• Each year we are paid a fixed salary. With our accumulated money, we can do some combination of:
• Invest and receive some market rate of return.
• Spend as much of our money as possible to convert susceptible people to longtermists at a constant cost per person. Critically, we can only create as many longtermists as there are susceptible people.

I’m not going to go into depth analyzing this model, but you can play with it here. The key observations are:

• We can be effectively constrained either by the amount of money available or by the extent to which we can effectively spend it on longtermists.
• Maximizing the number of longtermists at time t may require some amount of spending on movement building early on.

What should we take away from this?

This model above could be unrepresentative in many ways-- it’s not clear that movements can be modeled well as growing proportionally to their current size, we don’t have to spend money to convert people, etc. But it does gesture to some real aspects of the world:

• Generally, people are more susceptible to new ideas when more of the people around them actively endorse those ideas.
• There are important actors who we cannot affect through money alone, but could if the movement were bigger. For example, I don’t know of a good way to spend money to cause current key political figures to pivot into longtermism, but in a world where longtermism becomes a large social movement, younger people or the children of longtermists could hold key positions.

As such, I think we should consider treating movement growth as a compounding resource that is useful in and of itself and is not fungible with money.

This doesn’t necessarily imply that the marginal dollar put towards movement building now is better than investing (and even in the simplified illustrative model a large fraction of total money should often go to investing). But I think we should take it into consideration when thinking about the effects of our donations.