The ban targets software companies RealPage and Yardi. "RealPage has exacerbated our rent crisis and empowered corporate landlords to intentionally keep units vacant. So we're taking action locally to ensure our working renters can afford to live here," Peskin said.

RealPage and Yardi "collect and combine proprietary large landlord data and make pricing and occupancy recommendations," Peskin's office said. "These recommendations then effectively become the lay of the land, with multiple investigations finding they amount to illegal price-fixing. RealPage's own executives have told investors that its software has driven double-digit increases in rents, increased 'turnover' of units, and increased vacancy rates."

limited liability rental market collusion, there's an app for that