@KCVelaga_WMF noticed that the "monthly editors" metric in the [wiki comparison tool](https://docs.google.com/spreadsheets/d/1a-UBqsYtJl6gpauJyanx0nyxuPqRvhzJRN817XpkuS8/edit#gid=1183931625) are considerably higher than the equivalent number in Wikistats, in some cases by as much as 20%.
We should figure out what's going on here.
| period | wiki | Wikistats | Wiki comparison
| ---- | ---- | ---- | -----
| Jan–Dec 2020 | English Wikipedia | [131,860](https://stats.wikimedia.org/#/en.wikipedia.org/contributing/editors/normal%7Ctable%7C2019-12-17~2021-01-08%7Ceditor_type~user%7Cmonthly) | 139,341 (+5.7%)
| Jan–Dec 2020 | Spanish Wikipedia | [17,157](https://stats.wikimedia.org/#/es.wikipedia.org/contributing/editors/normal%7Ctable%7C2019-12-17~2021-01-08%7Ceditor_type~user%7Cmonthly) | 19,042 (+11.0%)
| Jan-Dec 2020 | Wikimedia Commons | [34,702](https://stats.wikimedia.org/#/commons.wikimedia.org/contributing/editors/normal%7Ctable%7C2019-12-17~2021-01-08%7Ceditor_type~user%7Cmonthly) | 41,917 (+20.8%)
To investigate:
[] Are the differences due to deletion drift? (see https://meta.wikimedia.org/wiki/Research:Wikistats_metrics/Editors) The data in the Wiki Comparison dataset was pulled in early 2021, and pages have been deleted since then
[] Are the differences due to different ways data may be filtered? (e.g. according to https://meta.wikimedia.org/wiki/Research:Wikistats_metrics/Editors, Wikistats explicitly filters out editors from Russia)
[] Is there an error in the code that calculates monthly editors in the wiki comparison, or in wikistats?