Ariana Tobin

The ability of advertisers to deliver their message to the precise audience most likely to respond is the cornerstone of Facebook’s business model. But using the system to expose job opportunities only to certain age groups has raised concerns about fairness to older workers. Several experts questioned whether the practice is in keeping with the federal Age Discrimination in Employment Act of 1967, which prohibits bias against people 40 or older in hiring or employment.

In February, Facebook said it would step up enforcement of its prohibition against discrimination in advertising for housing, employment or credit. But our tests showed a significant lapse in the company’s monitoring of the rental market. Last week, ProPublica bought dozens of rental housing ads on Facebook, but asked that they not be shown to certain categories of users, such as African Americans, mothers of high school kids, people interested in wheelchair ramps, Jews, expats from Argentina and Spanish speakers.