Data can be manipulated in many ways to show the results you want.
I will state that I have not taken the time (yet) to read this entire thread.
I do know a couple things.
1) I am a scientist and have degrees in Animal Science
2) I like the flavor and dark color of my "yard eggs"
3) "free range" has been debated.
a) The definition, as stated is "the opportunity to go outside"
i) my chickens love going out to the bigger pen and forage
ii) Commercially raised chickens (that make our eggs and poultry affordable to the general public) when given the opportunity will RARELY go outside, not sure why. so, most claims of "free range" eggs or poultry (when not from an individual) while they meet the USDA definition of free range since they have been given the opportunity to go outside, rarely do and are little, if any different from the standard poultry.
so the “FREE RANGE: Probably the most misunderstood of all claims, it’s important to note that hens basically stay near their food, water and nests, and the idea of a happy-go-lucky bird scampering across a field is far from the natural way of life. The claim only means that the hens have access to the outdoors, not that they avail themselves of the opportunity." is TRUE! (seen it myself)
4) nutritional value of eggs can be manipulated to resemble free range yard eggs with feed supplements.
This gets away from the original question (from 2011) which is free range only with no feed. I agree that todays chicken will likely need at least a little supplemental feed, esp. in the colder month.
I agree with your assessments as I have witnessed that myself.
While I don't have an Ag degree, I have a lot of 4H science under my belt as well as helping a daughter go through Vet Tech school (from which I picked up a lot as we used my flock for her studies), and of course my personal observations and rural upbringing.
Chickens will respond to their environment as conditioned. I note that my broody raised chicks have little problem integrating with the flock and transitioning to yard foraging while my artificially brooded chicks would rather stay in their box than venture outside....they are actually terrified by the "big outdoors" and not overly sure what to do with a bug the first time. I have to slowly transition them with pens until they are acclimated.
As noted before, my predominantly feed fed chickens prefer feed more than nice, wonderful, organic vegetables I can get for free from an organic grocer as his culls and toss. I stopped doing that as I kept throwing away a large portion of the bin as the chickens were so picky at what they would and wouldn't eat. The grocer noted that those who seem to make this really work have to feed only greens to young chicks before they develop a taste for grain feed. Since I only want to supplement greens and am not interested in replicating the wheel and having to carefully figure nutritional values for a balanced diet for my birds, as nutritional deficiency can cause a lot of harm in your bird, I find it easier to let the Ag science people behind the feed company do it for me. Years of testing have gone into those feed bags to provide optimal nutrition for poultry. And the feed companies are responsive to public concern. If I want to pay more, I can get organic, non-soy and non-GMO feed, but then my expenses rise further creating a bigger gap between what it takes to produce an egg and what I can sell an egg for, or how much I really want to spend for my own eggs.
On that thought, I'd also like to give a shout out to all those hard working poultry farmers out there who bring us Americans overall excellent food for very cheap prices. The public gets what it wants. The Ag community does not foist product upon them. People only want to pay about $1.50 to $2 for a dozen of commercially raised eggs whose nutrition value is well above sustenance level (and carefully marked on each egg carton per USDA standards). Most people don't want to pay/can't pay the $6 to $7 a dozen for organic, real pastured raised eggs with a bit more nutrition. (Those are the rates in my neighborhood). I'm sorry, but when I go to those nice, natural, whole food stores where I live (which I do have fun shopping at for some special items), I can't help but chuckle at all the newer BMW's, Lexis, and Audi's in the parking lot. Where I live, you have to go to a regular grocery store to see a better representation of all makes/models/years. If I really want to feel like 'home," I drive out to a rural Ag feed store to see those familiar beat up but still running Ford trucks.
I keep chickens as a hobby and sell a few eggs at $4 a dozen to offset feed costs. Note, that is offset feed costs. I would have to charge $6 a dozen or more to pay for my feed and supply costs with my little acreage as my chickens are predominantly fed by commercial grain feed, supplemented with yard foraging (which I make as rich as possible) and table scraps...and still provide me with darker yolks and thicker whites....which color I've found I can also manipulate by which brand of feed I give them. (Feed them Penny Royal, and you get green eggs with your ham.) But I find it hard to get anyone to pay more than $4 a dozen for farm fresh eggs. That seems to be the niche market price for me....and that tanks when the economy tanks. People are back to eating those commercial, cheap eggs again, and I've got eggs stockpiling in the fridge.
My vet tech daughter married a farmer who is an organic vegetable farmer in Tennessee. He grows absolutely gorgeous vegetables, and they have begun to raise chickens (starting with a small flock of hens I gave them...yup they pulled them behind an old Ford truck cross country from momma's coop to theirs) and increased each year with chicks and purchases. My son-in-law agrees with me that you have to have substantial foraging to be able to match (expense wise) the incredibly low prices people want to pay for eggs when you are a small holder. They have worked a system of tractor use wherein they pull the chicken tractor to different locations on the farm to both forage the birds and debug and fertilize the crops, being mindful of some plants the birds will also eat. Even so, they find it hard to be competitive in the egg market at their farmer's market stall. The chickens are still mostly for their own use and fertilizer for the farm.
So a number of sub-threads have been implied alongside the first question of whether 100% forage only would work, and the pressure to do that by certain perceptions of some customers. If you have large enough field, yes, maybe, in summer months...but you won't be doing that for real egg production as you would have a nightmare collecting eggs and most of us have a real threat of predators. (I constantly battle with hawks in my area and have to string hawk netting and wire to protect my birds). You also probably won't be producing the most optimum birds as they scrape for their living and therefore less egg output. I agree with another poster who said there is a difference between survival and optimum health.
So I think the real question is why would you want to 100% forage? Is it for the health and welfare of the chicken? Or for the perceived tastes of some customers who may not be basing their decisions on Ag science or nutritional truth but more from philosophical ideology?
I think the answer lies in what is evolving over time...."happy" birds seem to lay better and have fewer losses than "unhappy" birds which typically means those who have a pleasant amount of sunlight, safe forage, greenery, supplemented by well balanced, scientifically tested feed to produce optimum eggs and meat year round....but not necessarily at the cheapest price. This will always be offset by the customer who is looking for the optimum egg and the cheapest price.
My 2 cents.