How can the sudden drop in Organic Search, Social, Paid search, Referral channel sessions in months of September, October, November, and December be explained?
Due to the data layer implementation project that we did in second half of 2019, we updated default channel groupings in GA and introduced new channels (Local, Directory, Meta Search, Organic Social, etc.) to have Omni-channel attribution. Some data from these channels now appears in newly introduced channels and hence you’re seeing a drop in data.