I thought the article did a reasonably good job of addressing most of the confounding factors I thought of. My first guess was that this would be like populatio

I thought the article did a reasonably good job of addressing most of the confounding factors I thought of. My first guess was that this would be like population growth which is low when countries are poor (due to high infant mortality or things that correlate with being poor like civil wars), high as countries are getting richer (combining high fertility with lower infant mortality), and lower in developed countries (apart from immigration; fertility may be below replacement rate). But then we see the US continuing to eat more meat per capita into recent times. My other guess would then be that the US is consuming more food per capita (obesity and suchlike) but this doesn’t really line up with the relatively poorer Spain eating similar amounts of meat. It may still be possible that the peak was recent (the data given isn’t so fine-grained) and so we don’t see a decline from 1970 levels or that there are other confounding factors, eg maybe Spain’s statistics are including meat consumed by tourists. Tourism has increased a lot since 1970, I think, and tourists seem likely to eat a lot of meat. But it certainly doesn’t seem that falling meat consumption is anywhere near as universal as falling fertility as countries get/remain rich.