Thanks for engaging, James! I agree with all these limitations: we flagged several of them from the start and have mentioned others elsewhere. The only points I'll add are:

1. The uncertainties cut in different directions. For instance, correcting for the "understudied species" problem would give us higher welfare range estimates for some animals, like fish and flies, whereas correcting for the "scalar not binary traits" problem would give us lower estimates. It's an open question how those corrections would net out. But almost certainly not at the precise numbers we gave! (That's one of many reasons why I've never taken the precise numbers all that seriously.)
2. One of many comms failures associated with the Moral Weight Project is that we didn't do enough to stress the background considerations that led us to set up the MWP the way we did. The models are toy models; no one should trust them on their own. They make sense, insofar as they do, in the context of (a) more general arguments for thinking that, given hedonism, we're likely to end up with small differences between species, and (b) a particular view about how best to navigate the uncertainties associated with making these estimates in the first place (basically, defaulting to an approach that minimizes differences we can't justify, which we discuss both in the original post and in the book). If you think that, conditional on hedonism, nonhuman animals probably aren't that different from human animals and that we shouldn't give our priors that much weight, so the burden of proof is on any postulated differences, then I think what we did makes some sense.
3. I agree: low confidence is the right orientation. That being said, we should have low confidence in the alternatives! We're all fumbling in the dark here. My hope is just that we can, as a community, do better over time.

If you’re interested in this work, then let me point out that RP is hiring. 

I don’t think it’s worth doing. I don’t think we’d learn anything from the exercise. Skepticism about nematode sentience is driven partially by doubts that they achieve the same behaviors via the same mechanisms. So just establishing sameness of behavior wouldn’t be that helpful. The  research agenda for them should focus on how more complex brains achieve the same kinds of things, which might shed light on whether those brains are meaningfully different from simpler ones. Or so I’m inclined to think at this point. 

Guillaume would know better than me! I don’t know how long he spent on this project. 

Thanks for your work on this, Guillaume! I should stress that I think of $100K per criterion as the minimum that funders should expect to spend. And as you mention, some criteria are going to be much more expensive to investigate than others. In particular, the behavioral ones that you take to be the most evidentially significant could each cost 3x-5x that baseline. Behavioral work is hard!

I don’t know whether soil microarthropods are the most important to determine the expected change in welfare, but I was assuming that they are when describing biofuel subsidies as attractive to people who are sufficiently  suffering-focused. You’re right that other animals could be instead. 

Hi Vasco. No, I am not confident that biofuel subsidies decrease the population of invertebrates. These are shallow investigations and I expect that additional research would change our minds about many of the conclusions that people reached. 

Oh sure. I would certainly run one on ant or termite welfare for $50,000, again only speaking for myself and needing to talk to the board before it is a claim about what the organization would do. Possibly less. It’s just important to have enough to be able to support a handful of small projects. 

That is a hard question. I think the truth is that you could easily spend several hundred thousand dollars just to get decent evidence of any one of the eight Birch criteria being met in a single species. Trying to get evidence good enough that would allow you to make generalizations about soil animals is certainly a multi-million-dollar project. So, I am very concerned that any gettable number is too low to provide the kind of evidence that I would trust. That said, and speaking only for myself (not the board), I'd be willing to run a grant round for $100,000. I'm not sure about numbers lower than that.

Thanks, Vasco. If by “robustly” you mean either “clearly” or “under a wide range of moral assumptions,” then no, I don't think it's obvious that any of these interventions robustly increases total welfare in expectation when you account for soil animals. If you were sufficiently suffering-focused, then the third shallow, on biofuel subsidies as a mechanism for reducing invertebrate populations, would be quite appealing even when you account for soil animals. But I know that isn't your position.