All of Michiel's Comments + Replies

I think it's worth trying to have a toy model of this, even if it's mostly big boxes full of question marks. Going down to the gears level can be very helpful. For example, it can help you answer questions like "how much good does doing X for one person have to do for this to be worth it?", or "how many people do we need to reach for this to be worth it?". You might also realise that all your expected impact comes from a certain class of thing, and then try and do more of that or measure it more carefully. Which externalities to include is a tough question! In most examples I think there are a few that are "obviously" the most important, but that's just pumping my intuition and probably missing some things. I think often this is a case of building out your "informal model" of the project: presumably you think it will be good, but why? What is it about the project that could be good (or bad)? If you can answer those questions you have at least a starting point. One final thing: when I say "negative externality" I mean something that's actively bad. It seems unlikely that people using your platform for ineffective projects is bad, but rather neutral (since we think they're not very effective). What might be bad could be e.g. reputational damage from being associated with such things.