Facebook warns it is ‘underreporting’ iOS ad results amid Apple privacy changes

Facebook Inc said on Wednesday it is underreporting the results of its advertising business on Apple Inc iOS devices, acknowledging that recent privacy changes from the iPhone maker have made it more expensive and difficult for brands to advertise on Facebook.

Shares of the social media giant were down 3.7% at $344.32 in morning trading.

Facebook said in a blog post it estimates it is underreporting “conversions,” an industry term that includes buying of products or other actions a person takes after seeing an ad, by 15%, adding that the figure varied among individual advertisers.