Attorney general Kamala Harris was joined by attorneys from Los Angeles and San Francisco in suing the company last week for alleged violations of the state’s Unfair Competition Law, False Advertising Law and Unruh Civil Rights Act.

PPMs were introduced in 2008 and the lawsuit complained that radio stations serving primarily African American and Latino audiences were disproportionately affected by the methods Arbitron initially used to recruit PPM panellists. It said that of the 18 stations serving minority audiences in Los Angeles, 16 experienced ratings decreases in excess of 30% under the initial PPM system while three of those fell by over 70%. One station serving a mostly African-American audience was rated zero for a significant portion of the day.

Under the terms of a settlement agreed this week, Arbitron will pay $400,000 to the plaintiffs and will make changes to its respondent recruitment methods. Address-based sampling will increase to 65% of its recruitment activity to better capture households missed by landline recruitment methods, and country-of-origin questions will become a standard demographic characteristic collected from Hispanic households. The settlement also calls for “all reasonable steps” to be taken to increase minority participation in five of California’s major media markets.

Many of the requirements of the settlement have already been fulfilled, Arbitron said. It denies any wrongdoing.

Attorney general Harris said: “This settlement ensures that California’s diverse audiences will be fully counted by Arbitron’s ratings systems and that broadcasters serving these communities will have the opportunity to compete fairly in the marketplace.”