In England, cage-free-egg sales have now surpassed conventional-egg sales. Soon cage-free eggs will be all that’s produced across Europe, thanks to a decision to ban battery cages by 2012 in all E.U. member states.

Here in this country, large corporations are testing the same waters: Ben and Jerry’s is using cage-free eggs, and a small percentage of Burger King’s and Wendy’s eggs now come from cage-free chickens.

California’s Proposition 2 (which does not ban cages but demands they be larger than a standard battery cage — not quite cage free but certainly a movement in that direction) passed last fall with a wide margin.

On a continuum, the next step following cage free is free range, a term unregulated for egg production (or pork or beef); USDA free-range rules apply only to poultry production. They require outdoor access be available to a chicken for an “undetermined period each day”; they do not say how much space there should be outdoors, or that the chicken must go out or even be aware that it could do so. Presumably, this wouldn’t square with the mental image conjured by the term “free range.”

Some research says the free-range lifestyle is not really beneficial for either the consumer or the chicken. Swedish researchers recently found that bacterial infections (such as E. coli) can be more of a problem with free-range chickens. They have seen an increase in mortality since Swedish farmers left cages behind. Bacterial infections were the most common cause, and free-range chickens had more of them, in addition to more parasites and viruses, than their caged counterparts did. Free-range chickens also had more problematic encounters with other chickens, including violent pecking and cannibalism. A few months ago, a controversial New York Times op-ed cited a study suggesting that free-range pigs are also exposed to more parasites and bacteria.

Advocates, meanwhile, tout superior taste and even nutritional value of free-range products; other issues, such as antibiotic and hormone usage, can also factor into the equation, since much free-range food is likely to be raised under regimens that eschew those interventions. But it’s probably safe to say the main reasons most people buy cage-free eggs or free-range meat are beliefs about the well-being of the animals involved: It allows the animals, they say, to live more natural, maybe even happier, lives. One online commenter summed it up succinctly: “We don’t want to be kept inside always, so why would the animals?”

It may be tempting to dismiss such anthropomorphizing, but it’s harder to argue with the emotional impact that the sight of chickens crammed into cages can have on consumers. Harder still is determining when a chicken really is happy. Industry tends to respond with science: Studies have not revealed a difference in the levels of stress hormones in chickens raised in cages or outside.

Nevertheless, some consumers continue to hate the thought of chickens in cages. But cage-free eggs and free-range meat do cost more, and that expense, as well as space limitations (especially for beef), seem likely to keep a ceiling on the free-range market. Even California’s Prop 2 left the door open for cheaper battery-cage eggs to be imported to the state. On the other hand, Prop 2 might be a harbinger of a growing consumer sentiment  —  the emotions that drove it have not gone away.