Facebook proves, yet again, that it's terrible at math

Facebook has announced yet another measurement error, the fourth time the company has come forward to admit a discrepancy in its calculations since September.  SEE ALSO: Facebook’s fake news fix comes way too late This time the error involved undercounting traffic from publishers who used Instant Articles, the platform where media outlets post content directly to the social network. Facebook said a software update caused mobile traffic from iPhone users to be undercounted from Sept. 2