Facebook’s ad targeting algorithms automatically skew the delivery of ads based on race, gender and other characteristics, even when advertisers specify they want to reach a broad and neutral audience, a new academic study has found.

Researchers from the University of Southern California, Northeastern University and Upturn, a non-profit advocacy group based in Washington DC, also claimed that both the advertiser’s budget and the content of the ad each “significantly contribute” to the skew of Facebook’s ad delivery.

“Critically, we observe significant skew in delivery along gender and racial lines for ‘real’ ads for employment and housing opportunities despite neutral targeting parameters,” they wrote in a paper entitled Discrimination through optimization: How Facebook’s ad delivery can lead to skewed outcomes.

The release of the study, which has yet to be peer reviewed, comes a week after the US Department of Housing and Urban Development charged Facebook with violating the Fair Housing Act for “encouraging, enabling and causing housing discrimination” via its ad platforms.

The study said that researchers and journalists have found many ways in which advertisers target or exclude particular groups who see their ads, but suggested less attention has been paid to the implications of the ad delivery process.

To that end, the researchers spent more than $8,500 on Facebook ads, using different creative, copy and budgets, and then checked to see who received them.

Among the findings, they discovered that ads for jobs in the lumber industry reached an audience that was 72% white and 90% male, while ads for supermarket cashiers reached an audience that was 85% female, and ads for positions at taxi companies reached a 75% black audience – even when the researchers set identical targeting options.

A similar pattern emerged with entertainment ads, with Facebook delivering an ad for country music to an 80% white audience, while just 13% of white audiences were served an ad for hip hop albums – again, even when the ads had identical targeting parameters.

Ads also appeared to be skewed when it came to housing, such as whether a house was listed for sale or rent or included photos of a white or black family.

“Our results demonstrate previously unknown mechanisms that can lead to potentially discriminatory ad delivery, even when advertisers set their targeting parameters to be highly inclusive,” the researchers concluded.

However, Facebook said in a statement: “We stand against discrimination in any form. We’ve announced important changes to our ad targeting tools and know that this is only a first step.

“We’ve been looking at our ad delivery system and have engaged industry leaders, academics and civil rights experts on this very topic – and we’re exploring more changes.”

Sourced from University of Southern California, Northeastern University, Upturn; additional content by WARC staff