Several large landlords allegedly colluded in an effort to keep apartment rents high, including by using an algorithm that influences prices, according to new legal filings by the Colorado attorney general,

Attorney General William Tong joined the US Department of Justice and attorneys general from nine other states in a lawsuit this week against six of the nation’s largest landlords over their use of algorithmic pricing software to set their rental rates.

The complaint alleged the six companies set their rents using each other's information by either speaking with competitor's senior managers, calling around, and participating in user groups to discuss how to modify pricing methods.