I think this analysis should make more transparent its reliance on something like total utilitarianism and the presence of a symmetry between happiness and suffering. In the absence of these assumptions, the instances of extreme suffering and exploitation in factory farming more clearly entail "approximate veg*nism."

Consider the fate of a broiler chicken being boiled alive. Many people think that such extreme suffering cannot be counterbalanced by other positive aspects of one's own life, so there is really no way to make the chicken's life "net positive." Moreover, many moral positions deny that the extreme suffering of one individual can be counterbalanced by positive aspects of others' lives. So even if most farmed animals did have lives better than non-existence, we might still find the whole practice objectionable because of how it affects the worst off. Looking beyond just pain and pleasure, many perspectives object to our instrumentalization and exploitation of other sentient beings, which is inherent to the practice of animal farming. And there are also those who subscribe to some sort of asymmetry in population ethics, in which case the creation of negative lives is more bad than the creation of new lives is good (which weighs strongly against a practice like factory farming, even supposing that the average life is net positive).

I'm not saying that these are all correct, but rather that we should do a better job of clarifying our background assumptions rather than just saying "EAs should..."

I think your discussion of concentration camps in the comments further highlights the need to look beyond one particular moral perspective. Even if you are right that most lives in concentration camps were better than non-existence, many people would probably find objectionable the idea of "sentience-maximizing concentration camps," i.e. supporting the creation of new lives in concentration camps while simultaneously working to make them slowly better, rather than altogether banning the practice (supposing that these are the only two options). Again, this could be motivated by the sort of positions I mentioned above.

Welfare Footprint Project has, in my view, the best analysis of the (physical and psychological) pain farmed chickens go through on average under conventional factory farm conditions (and with specific welfare improvements). 

Here are the pages for:

1. Egg-laying hens.
2. Chickens raised for meat (excluding transportation and slaughter, which seems very bad in live shackle slaughter, with birds' bones frequently broken; WFP is also looking into slaughter).

They don't cover "goods" in their lives, but you could come up with estimates/ranges for these based on life expectancies and the kinds of goods you might expect, their durations and frequencies. Their life expectancies are:

1. 1.5-2 years for egg-laying hens.
2. 40-60 days for chickens raised for meat (other than broiler breeders, who live 1.5-2 years and are probably chronically hungry with conventional breeds).

They define 4 categories of intensities of pain: Annoying, Hurtful, Disabling and Excruciating. To summarize the definitions from this link:

1. Annoying pain can be ignored most of the time and results in little behavioural change.
2. Hurtful pain prevents engagement in positive activities with no immediate benefits like play and dustbathing, and animals with Hurtful pain would be aware of this pain most of the time, although can focus on other things and sometimes ignore it.
3. Disabling pain can't be ignored and is continuously distressing.
4. Excruciating pain is not tolerable. It can lead to extremely reckless behaviour to end it, e.g. exposure to predators, loud vocalizations. Things like scalding and severe burning.

Assuming symmetric ethical views, I would guess all of their pleasures (and other goods) would be at most as good as "Hurtful pain" can be bad, because "Disabling pain", by definition, can't be ignored and prevents enjoyment/positive welfare (of the kind they typically experience, presumably), and intuitively the kinds of enjoyment/positive welfare they can experience in factory farm conditions do not seem intense to me.

The kinds of pleasures I might expect in chickens would be from eating, comfort/rest and maybe just interest in things happening around them. Given the environments in conventional factory farms, I don't expect play, mating or parenting. Maybe chickens farmed for meat dustbathe (egg-laying hens in conventional cages wouldn't). I don't know if they form positive social bonds in these environments, but they might cuddle or preen/groom each other. I don't know if preening/grooming is enjoyable for chickens (I haven't looked into this). Maybe they can imagine things (visually or otherwise), and derive enjoyment from that. Maybe they enjoy some of their dreams, but presumably their dreams could be bad, too.

Thanks for the post — I only sort of skimmed the post and comments, and crucially I don't think this is  what your post is really about, but it seems like you have the view that we're kinda clueless about whether factory farmed animals have good or bad lives. In reference to this, you mention in a comment: "It's hard to be confident of any view on this, when we understand so little about consciousness, animal cognition, or morality."

As an aside, the term "factory farmed animals" is kind of weird category that includes both cows and chickens (among other animals). You could plausibly make the case that cows have net positive lives, but it seems pretty difficult to say the same for chickens.

Sure, we don't understand everything and everything about morality, but given the evidence we do have with regards to animal suffering and a few other basic axioms and intuitions, it seems hard to put this at 50:50 or similar. There are a bunch of arguments in favor of factory farmed chickens having bad lives, and I'm not aware of many arguments saying that they have positive lives. I think the Holocaust case is interesting but a bit confusing because those people had (probably) happy/positive lives before the Holocaust, and could have had happy/positive lives if they had been released. If someone were to intentionally breed humans into existence in order to place them into concentration camps (and later kill them), I think most plausible ethical theories would consider this to be uncontroversially bad.

For comparison, from Rethink Priorities' 2019 EA Community Survey:

I realize this is a bit hypothetical but it does seem like the numbers matter a bit, so I want to ask:

Is there some basis on which you're imagining 50% of folks in an animal welfare EA group think that if factory farmed animals are moral patients, it's more likely that they have net-positive lives?

That surprised me a bit (I'd imagine it close to 0%, but I'm not too active in any EA groups right now, especially not any animal-focused ones so I don't have much data).

Note that there might be other crucial factors in assessing whether 'more factory farming' or 'less factory farming' is good on net — e.g., the effect on wild animals, including indirect effects like 'factory farming changes the global climate, which changes various ecosystems around the world, which increases/decreases the population of various species (or changes what their lives are like)'.

It then matters a lot how likely various wild animal species are to be moral patients, whether their lives tend to be 'worse than death' vs. 'better than death', etc.

And regarding:

The number would be much higher than 60% on strictly utilitarian grounds, but humans aren't strict utilitarians and it makes sense for people working hard on improving animal lives to develop strong feelings about their own personal relationship to factory farming, or to want to self-signal their commitment in some fashion.

I do think that most of EA's distinctive moral views are best understood as 'moves in the direction of utilitarianism' relative to the typical layperson's moral intuitions. This is interesting because utilitarianism seems false as a general theory of human value (e.g., I don't reflectively endorse being perfectly morally impartial between my family and a stranger). But utilitarianism seems to get one important core thing right, which is 'when the stakes are sufficiently high and there aren't complicating factors, you should definitely be impartial, consequentialist, scope-sensitive, etc. in your high-impact decisions'; the weird features of EA morality seem to mostly be about emulating impartial benevolent maximization in this specific way, without endorsing utilitarianism as a whole.

Like, an interest in human challenge trials is a very recognizably ‘EA-moral-orientation’ thing to do, even though it’s not a thing EAs have traditionally cared about — and that’s because it’s thinking seriously, quantitatively, and consistently about costs and benefits, it’s consequentialist, it’s impartially trying to improve welfare, etc.

There’s a general, very simple and unified thread running through all of these moral divergences AFAICT, and it’s something like ‘when choices are simultaneously low-effort enough and high-impact enough, and don’t involve severe obvious violations of ordinary interpersonal ethics like "don’t murder", utilitarianism gets the right answer’. And I think this is because ‘impartially maximize welfare’ is itself a simple idea, and an incredibly crucial part of human morality.

I find it easy to follow a strictly vegan diet outside of eating at restaurants. At restaurants (which I don't go to that often) and on family holidays I concede to eat whatever is available. For the past few weeks and for another few weeks I will be eating animal products because I am volunteering for a study that requires me to be on a meat-eating diet. The study is studying a benzodiazepine drug. I am only doing this because the study will pay between $3,000 and $15,000. I am compromising my vegan diet as a one time thing. To me, it seems that compromising the vegan diet for a short amount of time is worthwhile if I will get a few thousand dollars.

Regarding animals' lives, it seems that their sentience and their experience is an extremely hard mystery to solve. I don't even remember what I was experiencing when I was in the womb and the first few years of my life, let alone what another creature is experiencing during the same first few years of their lives which for them comprises the entirety of their lives (in the case of chickens). 

Maybe a useful way to think morally about this is this hypothetical scenario:

We have found an arcane gas station in the middle of the desert. The pump itself and the ground around it is impenetrable and unable to be taken apart. Therefore, its inner workings are inaccessible. The gas from it is incredibly efficient. A gallon of it amazingly will power any car or truck on the road for 100,000 miles. Every time gas is pumped from it,  the sound of humans screaming in immense pain can be heard. We don't know whether humans are suffering at the expense of us having the miraculous gas. It is bothersome because it seems like we should be able to figure out what is going on. However, because this is an arcane gas pump seemingly left for us by some magical power, that is much easier said than done. Should we keep using the pump?

PS: I can easily go without eating food from restaurants. I only go for social reasons. Strategies to avoid meat at restaurants could be only ordering a beer (and perhaps having a nutritious snack beforehand) or ordering salads that are comprised only of vegetables.

I would expect "Anything goes. A normal meat-eating diet, optimized only for health and convenience." to be a reducetarian diet in practice compared to the average diet for most people in most developed countries, since I think the average person eats more animal products and too few plants than is optimal. I would guess that for most people, a roughly optimal diet for health and convenience could be found within the group "vegan except for dairy, bivalves and when it would be inconvenient", which also falls under Approximate veg*nism in places where most restaurants have decent veg options with protein or if you rarely eat food from restaurants, although there are other considerations. The main exceptions would be when getting food from a restaurant with no good veg options (or when in a group looking to order from such a restaurant, and you would otherwise try to persuade them to get food elsewhere).

When considering only the more direct effects on farmed animals and wild animals, the only animal products I would recommend replacing with plant-based foods would be from herbivorous* factory farmed animals roughly the size of turkeys or smaller, other than bivalves and similarly unlikely to be conscious animals, so

1. Factory farmed poultry (chickens, turkeys, ducks) and their eggs
2. Herbivorous farmed fish
3. Herbivorous farmed invertebrates, other than bivalves and others with similar or lower expected moral weight
4. Herbivorous farmed amphibians and reptiles, although relatively few people eat them often, anyway

This assumes their lives are bad on average, which is my expectation.

*What I mean by "herbivorous" here is that their diets while farmed are almost exclusively plant-based. Also, I would add if their diets are herbivorous except for animal products from farmed animals, themselves on the above list, and maybe extend this further.

I'm personally bivalvegan, i.e. vegan except for bivalves, and plan to stick with this.

I'd guess the most controversial part of this post will be the claim 'it's not incredibly obvious that factory-farmed animals (if conscious) have lives that are worse than nonexistence'?

But I don't see why. It's hard to be confident of any view on this, when we understand so little about consciousness, animal cognition, or morality. Combining three different mysteries doesn't tend to create an environment for extreme confidence — rather, you end up even more uncertain in the combination than in each individual component.

And there are obvious (speciesist) reasons people would tend to put too much confidence in 'factory-farmed animals have net-negative lives'.

E.g., when we imagine the Holocaust, we imagine relatively rich and diverse experiences, rather than reducing concentration camp victims to a very simple thing like 'pain in the void'.

I would guess that humans' nightmarish experience in concentration camps was usually better than nonexistence; and even if you suspect this is false, it seems easy to imagine how it could be true, because there's a lot more to human experience than 'pain, and beyond that pain, darkness'. It feels like a very open question in the human case.

But just because chickens lack some of the specific faculties humans have, doesn't mean that (if conscious) chicken minds are 'simple', or simple in the particular ways people tend to assume. In particular, it's far from obvious (and depends on contingent theories about consciousness and cognition) that you need human-style language or abstraction in order to have 'rich' experience that just has a lot of morally important stuff going on. A blank map doesn't correspond to a blank territory; it corresponds to a thing we know very little about.

(For similar reasons, I think EAs in general worry far too little about whether chickens and other animals are utility monsters — this seems like a very live hypothesis to me, whether factory-farmed chickens have net-positive lives or net-negative ones.)