> Nevertheless, the composition of audiences can still tilt toward demographic groups such as men or younger workers, according to a study published today by researchers at Northeastern University and Upturn, a nonprofit group that focuses on digital inequities

>One reason for the persistent bias is that Facebook’s modified algorithm appears to rely on proxy characteristics that correlate with age or gender, said Alan Mislove, a Northeastern University professor of computer science and one of the study’s co-authors.

Hypothetically, let's say that the trucking company in the article used "people interested in cars" as a targeted group. It would come as no surprise to me if this group was > 80% male.

It may even be by another mechanism- facebook's algorithm may look at the profiles of individuals that clicked through on ads in order to determine who to show the ads to in the future. This is a good way to provide cost effective advertisement. This also may be done in a way such that a small fraction of these ads are still shown to $membersOfProtectedClassX, even in cases where said class is statistically unlikely to click on the ad. What small fraction is necessary to be legally unproblematic?

If Joe Schmoe creates a facebook ad to hire for a bricklaying job (a job which is 98% male), what percentage of those ads must be served to women to be legally compliant?