I’m thinking more about this interpretation, but I’m not sure it is correct because WFP’s calculations are designed to be conservative in estimating the welfare improvements and exclude various welfare harms. For example, it looks like the broiler estimates exclude welfare harms from transport to slaughter. When these hours of suffering are added back in, the ratio between the two scenarios can go down.
As a hypothetical example, suppose BCC chickens are currently estimated to suffer 50 hours, while non-BCC chickens suffer 100 hours. If we add in 10 hours of suffering from transport for non-BCC chickens and only 2 hours for BCC chickens (as they are believed to be more heat tolerant), this ratio then increases to 53%. So while excluding harms from transport to slaughter is fine for keeping the absolute difference in hours suffered conservative (50=100-50 < 58 = 110-52), it does not necessarily keep the ratio conservative (50% vs 47% suffering reduction).
I think this is fine when comparing between different welfare levels for species, but I suspect it means they can not be used to compare directly to non-existence?
[Tagging @saulius as well since this seems relevant to the extent of whether cage-free is ‘still pretty bad’.]
Thank you, that’s all helpful!