Last week, Target, Denny’s, and Taco John’s vowed to start using cage-free eggs. The week before it was ConAgra, Mondelez International, and Norwegian Cruise Lines. Spurred by consumer demand and pressure from animal welfare advocates like the Humane Society of the United States (HSUS), these pledges are part of a recent landslide from more than 35 companies committing to using 100 percent cage-free eggs in the next five to 10 years.

It’s one of the most interesting cases of corporate peer pressure in recent times.

“This is going to be a case study in business school,” says Michael Liburn, a professor in the Poultry Research Center at Ohio State University. “It’s completely market-driven.”

Animal welfare is increasingly becoming a concern for large food corporations as consumers demand more transparency in their food system. Nearly 70 percent of companies globally now have published animal welfare policies on their websites, up from 46 percent in 2012, according to the annual Business Benchmark on Farm Animal Welfare (BBFAW).

Paul Shapiro, vice president of animal farm protection of HSUS, says that his and other organizations have targeted battery cages for chickens because they’re “the most severe form of factory farming in the country.” He sees his job not to convince Americans that animal cruelty is wrong—he thinks people are already sure of that on their own—but simply to show them that it is happening. “We don’t have to change anybody’s mind, we just have to inform them of what is standard practice in the egg laying industry,” he says.

Their strategy seems to be working. At the state level, many farmers in California have been changing their practices to adapt to the regulatory shift away from battery cages that went into effect in 2015 (based on Prop 2, a ballot measure that passed by 63 percent). Michigan, Oregon, and Washington have also all passed laws mandating more space for hens, and Ohio has a ban on new construction of battery cages.

And at the corporate level, every few days seems to bring the announcement of another switch. It’s happening in all sectors of the food industry, including fast food chains like Burger King and Subway; coffee shops like Starbucks and Peet’s; hospitality brands like Hilton and Carnival Cruises; foodservice companies like Aramark and Sodexo; grocery stores like Target and Costco; and conglomerates like Nestlé and ConAgra.

What’s behind this massive change, and what effects will it have on $10 billion egg industry? Here’s what you need to know.

Why cage-free?

The short answer is that conditions for hens in battery cages can be pretty horrific. The HSUS estimates that currently about 95 percent of eggs come from caged chickens, generally confined to a living space of 67 square inches, about the size of a sheet of paper. Stories of mistreatment are rampant–the hens can’t move or spread their wings, and often die of dehydration or abuse from birds around them.

“Cage-free” is a bit misleading, however, if you’re imagining that the chickens will be living a bucolic existence pecking out bugs in a farmyard. Unlike pasture-raised birds, most “cage-free” hens will still spend their entire lives indoors, in a large, crowded open space with hundreds of other birds. They may still have their beaks burned off, or trimmed, to prevent injury to other hens.

Though it’s not a perfect, Old McDonald’s farm solution, Shapiro and others see this movement as progress. “Cage-free isn’t cruelty free, but it does mean a significant improvement over battery cages,” he says.

What will farmers have to do to make the change?

Going cage-free requires farmers to stop using their current battery cage hen house equipment, which can cost millions of dollars and is supposed to last 15 years or more, and retrofit their barns to install a new, often equally expensive system. And because the new equipment can’t fit as many hens, some poultry farmers will need to build additional structures on their property to keep up production, which requires additional money and time to go through the zoning and permitting process. (Wired has a good flowchart of the issues facing farmers.)

“Consumers need to understand that a lot of these transitions can’t be done overnight,” says Dr. Ken Anderson, a professor in the Department of Poultry Science at North Carolina State University. “A lot of companies are driven by the same issues that we consider when we buy a new car: Is our old car depreciated out? Or is it worn out and we need to replace it right now? It’s the same considerations, just on a larger scale.”

What timelines are these companies working with?

For the reasons mentioned above, this conversion process may take a decade or more, which is why company timelines vary depending their suppliers and their egg needs. Currently, these are the corporations that have pledged to switch to cage-free eggs so far. (Note that these are promises the companies have made; it’ll be up to consumers to ensure they stick to them.)

By end of 2016: Shake Shack, Taco Bell, Bon Appetit Management Company (for its liquid eggs; shell eggs have been cage-free since 2005.)

By end of 2017: Au Bon Pain, Burger King, Hilton

By end of 2019: Compass Group

By end of 2020: Aramark, Arby’s, Barilla, Caribou Coffee, Einstein Bros. Bagels, Mondelez International (2025 in Europe), Nestlé, Panera Bread, Peet’s Coffee, Starbucks, Unilever, Wendy’s

By end of 2022: California Pizza Kitchen, Quizno’s, Royal Caribbean Cruises

By end of 2025: Campbell Soup, Carnival Cruises, Con Agra, Dunkin’ Donuts, Flowers Foods, General Mills, Jack in the Box (though plan to “transition the majority of our egg supply to cage-free by 2020”), Kellogg’s, McDonald’s, Norwegian Cruise Lines, Sodexo, Subway, Target, TGI Friday’s, Taco John’s

By end of 2026: Denny’s

TBD (have announced intention but not timeline): Cheesecake Factory, Costco, Hyatt, Michael Foods, Rembrandt Foods, Wal-Mart

Who’s missing from the list?

Major grocery corporations like Kroger and Safeway; Target is the only one that has committed to a date. Costco and Wal-Mart, two of the nation’s largest egg retailers, have both announced their intentions but have no timeline.

Major behind-the-scenes players like commercial processors and distributor Michael Foods and supplier Rembrandt have also announced their “commitment” to cage-free eggs, but haven’t released any numbers or timeline for what that commitment could look like.

What will this mean for egg prices?

They will probably go up a little bit—but just how much is still to be determined. A study in Massachusetts, where a referendum that would require all eggs sold in the state to be cage-free is likely to go on the ballot in November, estimates that prices for a dozen eggs could go up anywhere between 12 and 80 cents. A 2015 industry-funded study found that a dozen cage-free eggs cost about 15 cents more to produce, and those costs would almost certainly be passed on to the consumer.

However, Liburn cautions that other factors may go into rising egg prices in the coming years. “About 70 percent of your total production is feed cost,” he says. “Certainly the volatility of the grain markets will have a much greater impact on a year-to-year basis than the management system.”

Are there any other potential downsides?

Some in the industry, like Liburn and Daniel A. Sumner, director of University of California Agricultural Issues Center and professor at U.C. Davis, wonder if the cage-free system is actually the best alternative for battery cages. Larger furnished, or enriched, cages give hens more room to roost and peck than battery cages, but still have some of the benefits for farm operators, like an egg belt that keeps eggs away from contact with manure and other hens, and decreased dust in the air which can cause respiratory problems in workers.

The HSUS claims that all caged chickens carry a much higher risk of Salmonella, though there have also been studies done suggesting that the risk is much higher in a cage-free environment, where hens can interact with each other and there is more potential for eggs to come into contact with feces.

Hens can also become aggressive and cannibalistic when confined together, so farmers of cage-free hens will need to monitor behavior and there could be higher rates of injury and death in their flocks. Shapiro from HSUS says that in parts of Europe, where lawmakers have already banned battery cages, farmers saw some initial aggression but learned how to manage it with time.

Ultimately, these are the unknowns that many farmers will need to work out as they go. “A tremendous amount of research needs to be done so we can optimize the performance of the birds in the cage-free environment,” says Anderson of North Carolina State. He points out that there are only two research centers in the U.S. devoted to aviaries, and many of these question marks will eventually be answered with trial and error and careful monitoring.

“We’re going to be addressing a lot of these questions for a long time,” he says.