Thank you for the feedback Florian! I will move this issue upwards in my to do list since so many of you have explained the issues with WPM.

Thank you for this post. Really enjoyed your reflection. It was even more interesting than the actual question of what was right in the situation.

Multiple people suggested getting a simpler domain name. The website is now also accessible at foodimpacts.org.

Thank you for the feedback, Gina!

You are the first person to mention both culling of male chicks and fish who are fed to farmed salmon. You are correct that these are shortcomings. We must also be mindful of breeder chickens used in broiler farming. Unfortunately, accounting for all of these effects would be difficult and would require data that could be difficult to find. About your requests:

1. I will consider it.
2. I assume that understanding the impacts of eating wild animals would be even more difficult so for the sake of keeping it doable I would rather not venture there even though wild animal welfare is an important area to me personally.
3. Brian Tomasik has written an interesting in-depth article on this question and he remains undecided. It seems that this is unfortunately a fundamentally difficult question. It troubles me as well that I don't know much about such a sensitive parameter.

Thank you for the feedback Ramiro! Since people have asked so many questions about the results of this kind of analysis I was thinking about adding a FAQ section to the website. I could add the remarks about shrimp welfare there.

User RandomEA suggested here that there should be an option to use the number of animals consumed as part of a common diet instead of the current animals-per-2000kcal logic. Would you consider that a good solution to the issue that shrimp is realistically a delicacy?

Thank you for commenting, Devon. Culling of male chicks is not considered. Unfortunately the tool will not include every effect because that would be rather difficult. As someone pointed out the breeder chickens used in broiler farms are not considered nor are the fish who are killed to feed farmed salmon.

You are right. I spent time thinking about your comments and I agree that making the tradeoff clearer is one of the most important improvements I can make. Thank you for bringing it out.

Thank you Dominic! There is already a paragraph about transportation on the methods page of the website. I will add a paragraph about organic food as well.

Thank you for the feedback, MichaelStJules! I added all of your ideas to my todo list.

I definitely should have added probability of sentience to the model. I looked at Brian Tomasik's model which included sentience multipliers and I have read the OPP report you linked so I don't know why I didn't consider it.

Jason Schukraft's "Differences in the Intensity of Valenced Experience across Species" was great and I will be happy to study his other research. Thank you for linking to it.

I wish I was aware of kbog's post before I started. I managed to find multiple analyses of suffering but I didn't know someone had already devised a combined model!

Thank you for the thoughtful feedback, Benjamin! I will try to explain the model a bit more thouroughly than the methods section of the post.

Let's forget normalising and weights for a moment. If we measure suffering in hours/kcal and emissions in CO2eq/kcal then the subscales have different units and can't be added (unless we have a conversion formula from one unit to the other somehow). A common solution in this case is to multiply the subscale values. If we do this a 1% change in suffering changes the combined score by the same amount that a 1% change in emissions would.

We still might want to prioritise some subscales more than others. If we would have added subscale scores we could have multiplied the subscale scores by some constant weights beforehand. If instead we multiply subscale scores we would exponentiate the subscale scores by weights beforehand. This simple idea is called a weighted product model (WPM) in the multiple-criteria decision analysis discipline which studies how to make decisions when we have multiple conflicting criteria.

This tool uses a weighted product model. The unnormalised suffering and emissions scores are:
1. exponentiated by their corresponding weight,
2. multiplied together to get a combined score,
3. the combined score is normalised to the 0-100 range for cleaner display.

WPM is a dimensionless method used for ranking options when making decisions. That is, to answer questions like "is it more important to avoid chicken or beef" not "what is the cardinal utility of avoiding chicken". This model is only useful for prioritising if I have decided to reduce meat consumption but am only able to leave one species off my plate. I understand now that I should have made it more clear.

Somehow measuring the utility of leaving a species off my plate would be much more interesting but seemed difficult considering the time and skills I had. I did consider using something like DALYs. There is research on converting emissions to DALYs which would allow us to use a parameter for converting non-human animal DALYs to human DALYs but I decided for the simpler ranking-only model.