Meanwhile, local and federal authorities have launched antitrust probes to investigate how Compass may be harming real estate markets. Behind one probe is US Senator Elizabeth Warren (D-Ma.), who thinks Compass may be threatening to “create a two-tiered housing market where insiders pay for exclusive access to housing inventory and market data, while everyone else is shut out.”

An attorney who represents renters, Blake Hunter Yagman, told Ars that plaintiffs are looking forward to having their case heard in court.

“When a titan of an industry decides to choke off supply of an essential good or service, like housing, the implications can be swiftly vast and severe,” Yagman said. “New Yorkers already are facing affordability challenges which have evolved into a crisis—and that crisis is only compounded by high rent prices, which is the largest bill that most of us have to pay.”

Compass declined Ars’ request to comment.

But Zillow’s spokesperson weighed in on the class action complaint, telling Ars that, “when listings are deliberately hidden from public platforms, real consumers pay the price. This summer, New Yorkers have seen exactly that play out, with one dominant brokerage deciding which homes people get to see and further squeezing the NYC market during a housing crisis. Because StreetEasy exists to give every renter and buyer access to every available home, we support efforts to bring accountability to these practices.”

Rising rents linked to hidden listings

As regulators eye the situation, Compass’ fight with Zillow has already increased rents in New York, Castaneda and Gelfand alleged. For Castaneda, signing a lease for a one-bedroom in downtown Manhattan this August set his monthly rent at $5,270, which “far exceeds” what he might have paid if he signed his lease one month sooner when the “average/median asking rent price” in that area was $4,390, the complaint said.