FAQ: Everything Facebook has admitted about its measurement errors

To paraphrase J. Cole, Facebook messes up on its math one time; shame on Facebook. Facebook messes up on its math a second time; shame on those of us blindly trusting Facebook’s math. Facebook messes up on its math a third time; time to make a list of all the times Facebook messed up on its math. On three separate occasions since September, Facebook has disclosed more than a handful of errors related to its own measurements that brands, publishers and others use to evaluate the performance of their Facebook ad campaigns, Facebook-native videos, Facebook-only Instant Articles and Facebook Pages, as well as their off-Facebook mobile apps and websites. To help myself and anyone else keep track of these errors, here’s an itemized list of each error Facebook has announced to date, a (hopefully) normal-speak explanation of what the error was, whether Facebook has corrected it or plans to, how it has/will correct the error and what impact the error had on the measurements Facebook reported.