I have a nitpicky comment that may not be very important in the end.
It seems that estimates of how long cage-free and caged hens live and how many eggs they lay are partially based on Norwood and Lusk 2011. I once did that as well but I was told that the book describes small scale cage-free systems that don’t use optimal genetics. Large scale cage-free systems (which perhaps didn’t exist at the time to the same extent) are likely much more similar to current caged systems, especially after industry will have some time to optimize things. If it was the case that caged hens lay 467 eggs while cage-free eggs lay 325, I would be concerned about the higher number of pullets (hens who are too young to lay eggs) needed to produce the same number of eggs. I see that in your estimates you use a “Length of laying” variable, not a “lifespan” variable. I don’t know if “length of laying” includes the pullet phase, which according to industry breed specification requirements like this lasts about 17 weeks. If it doesn’t include the pullet phase, then you may be implicitly assuming that hens don’t suffer during the pullet phase or something. I failed to understand how exactly your estiamte works so I’m not sure. Anyway, I don’t know what the differences between cage-free and caged actually are. I was told by a vet that cage-free and caged birds have the same lifespan nowadays and saw a few indications that same breeds are used. But I also saw this article that claims that caged hens lay 500 eggs, while cage-free lay 420-430 eggs. I don’t know whom to believe. I can send you an unpublished document where I examined a few more sources but I’m still confused about it.
Anyway, in a way, this stuff doesn’t really matter that much for the estimate. Cage-free reforms may or may not increase the number of hens by say 5% (I’m saying a random number here because I don’t remember. If anyone’s decisions depend on this, I can try to write something about it). But if we use Welfare Footprint’s estimates, then it follows that the switch to cage-free reduces the suffering by like 60%, so that 5% doesn’t have that much impact on the final estimate. The biggest uncertainty is the years of impact. You chose 4 years but you could’ve also chosen 40 years and then everything would’ve been 10 times more cost-effective.
I have a nitpicky comment that may not be very important in the end.
It seems that estimates of how long cage-free and caged hens live and how many eggs they lay are partially based on Norwood and Lusk 2011. I once did that as well but I was told that the book describes small scale cage-free systems that don’t use optimal genetics. Large scale cage-free systems (which perhaps didn’t exist at the time to the same extent) are likely much more similar to current caged systems, especially after industry will have some time to optimize things. If it was the case that caged hens lay 467 eggs while cage-free eggs lay 325, I would be concerned about the higher number of pullets (hens who are too young to lay eggs) needed to produce the same number of eggs. I see that in your estimates you use a “Length of laying” variable, not a “lifespan” variable. I don’t know if “length of laying” includes the pullet phase, which according to industry breed specification requirements like this lasts about 17 weeks. If it doesn’t include the pullet phase, then you may be implicitly assuming that hens don’t suffer during the pullet phase or something. I failed to understand how exactly your estiamte works so I’m not sure. Anyway, I don’t know what the differences between cage-free and caged actually are. I was told by a vet that cage-free and caged birds have the same lifespan nowadays and saw a few indications that same breeds are used. But I also saw this article that claims that caged hens lay 500 eggs, while cage-free lay 420-430 eggs. I don’t know whom to believe. I can send you an unpublished document where I examined a few more sources but I’m still confused about it.
Anyway, in a way, this stuff doesn’t really matter that much for the estimate. Cage-free reforms may or may not increase the number of hens by say 5% (I’m saying a random number here because I don’t remember. If anyone’s decisions depend on this, I can try to write something about it). But if we use Welfare Footprint’s estimates, then it follows that the switch to cage-free reduces the suffering by like 60%, so that 5% doesn’t have that much impact on the final estimate. The biggest uncertainty is the years of impact. You chose 4 years but you could’ve also chosen 40 years and then everything would’ve been 10 times more cost-effective.