Hi Vasco, 
Thanks for the question and sorry for the slow reply. 

The overall process was to combine two estimates of THL's cost-effectiveness through weighting them in a Guesstimate model, along with some assumptions about the speed-up time of the intervention and the marginal cost-effectiveness relative to the past average cost-effectiveness. 
The more detailed steps were: 
1. Gather two estimates: THL review by ACE from 2025, wherein cage-free work has an estimated 2 to 44 hens affected per dollar (best guess of 11); THL self-published report from 2025, which reports 2 hens freed per dollar spent between 2015 and 2024. 
2. Make assumptions: The THL self-published report was conservative in that it didn't include a counterfactual speed up assumption. So, we assumed that the interventions THL carried out each affected 6 to 15x as many hens than reported on average through speeding up the timelines to hens becoming cage-free. Then, since the marginal cost-effectiveness in 2026 is probably much less than the average cost-effectiveness from 2015-2024, we discounted the resulting THL self-reported estimate by 70%. This is a rough guess.
3. In a Guesstimate model, I combined the two estimates (giving equal weight to each) to get an overall estimate of THL's cost-effectiveness on the margin (caveat below). (The ACE estimate was encoded as a lognormal distribution between 2 and 44 hens/$, which had a mean of 14 which is slightly better than their best-guess, which could be a median or mean, I'm not sure). This produced an estimate of 10 (3.6 to 29) hens/$. The method isn't perfect, since these estimates might not be independent so the variance could be artificially reduced, but for our initial version, we felt it was a good enough estimate (other factors matter more to the CCF). 

Upon looking back, I realize that I made a typo in the methodology -- it should be 3.6 to 29 chickens per dollar spent, not 3.6 to 22. So thanks for pointing my attention to this! I've now fixed it.

On the more important question, I agree that the marginal cost-effectiveness is definitely the important question, and I'd like to have this. However, the best estimates we could find for the first version of the CCF were for average cost-effectiveness of past spending. We plan to improve upon these estimates in the future, such as through considering more evidence. If you know of any good marginal cost-effectiveness estimates, or other cost-effectiveness estimates, please do link them below!

Hope this is helpful! Also, I'll look into how to change the settings so you can copy text, I'm not sure why it's like that

Thank you for writing this, Tom and Rocky. I think this is an important caution, and I appreciate the way you are framing it.

As someone directly involved in a welfare-tech-style intervention, I actually agree with much of your core argument. I also strongly believe that good tech interventions can be extremely impactful, partly for some of the reasons you outline: they can sometimes bypass certain barriers that exist for other welfare work, and they can make it possible to help very large numbers of animals relatively quickly. But I also agree that, when looked at from the outside, they can be falsely perceived as silver bullets, so I want to share three insights from SWP about electrical stunning for shrimp.

I’ve also posted a more direct response to “Animal Welfare Has an Evidence Problem,” which you refer to in the post, to clarify some of these points. 

First, at SWP, our work on shrimp stunning has been much more complex than simply deploying stunners at scale. The Humane Slaughter Initiative does involve getting electrical stunning equipment used on farms, but in practice, we are doing much more than that: coordinating and funding welfare research and R&D, collecting field data, working with scientists, developing and refining slaughter protocols, iterating on the technology with existing equipment providers, negotiating with industry, engaging corporate stakeholders, building and maintaining producer relationships, training staff, educating farmers… Much of this work is not visible from the surface, but it’s central to making the intervention possible. The tech matters, but it does not operate in a vacuum. 

Second, on shrimp stunning specifically, I think you captured something important. SWP entered this space aware that there were uncertainties, and we’ve been proactively trying to reduce them. Some of that work is public, but much of it happens through industry collaborations, field implementation, and producer relationships, which are often necessarily behind closed doors or covered by NDAs. That can make the work less visible from the outside, even though it is central to what we are doing.

This is one reason I think treating our intervention too simplistically, as merely putting stunners on farms, can lead to exactly the kind of disillusionment and backlash you describe.

Third, I feel some of the issues you describe are not limited to tech interventions. Many ambitious attempts to change existing systems seem to have an early phase where progress looks relatively fast, followed by a harder phase where problems become more complex, uncertainty can increase, coordination costs become bigger, and resistance from affected stakeholders becomes stronger. That does not necessarily mean the intervention – tech or otherwise – was a mistake; it can be a natural progression of an ambitious project. 

Thanks again for writing this! It’s an important reminder that welfare tech can be genuinely promising and, in some cases, extremely impactful, but it should not be treated as a silver bullet. 

I think that this diagnosis is basically on target; it points to something that seems relatively under-resourced, despite some focus by think tanks, and something that the major AIxBio safety groups are not as focused on. I also agree that we don't know if AGI will subsume this, and that it's plausible but uncertain if other bottlenecks matter more, but that's an uncertainty we can't resolve without simply waiting for the outcomes, and so this seems very high value in expectation. 

I'm less certain about the object level questions, and don't have strong intuitions - so I think that conditional on not hearing from someone more informed about this that there are additional questions or concerns, or literature you should look at, the best way to figure out whether this is needed, and what the risk is, is to start the work - good luck, and I'd be happy to chat about this more!