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.