Hi Tilman,

Apologies that it’s taken some time to get back to you. 

We had initially published these numbers as part of Katherine’s announcement on our website that she was stepping down. After you emailed, we went back through our data sources and discovered an error: the growth in engagement came from sources that used different definitions and filters. For 2015, only Wikipedias were included in the totals for pageviews[1] and active editors[2]; however, for 2020, our data included pageviews and active editors across all Wikimedia sites[3]. When we corrected for this error as well as an error related to data normalization, we saw that pageviews increased 24 percent (not 30 percent) over that time period[3,4], and active editors increased 18 percent, not 36 percent[3,5].

We have issued a correction for the website. Thank you for flagging this so that we were able to catch and correct this error!

Warm regards,

Kate

[1] December 2015 pageview data from  https://stats.wikimedia.org/EN/TablesPageViewsMonthlyCombined.htm

[2] December 2015 active editor data from https://stats.wikimedia.org/EN/TablesWikipediansEditsGt5.htm

[3] December 2020 content interactions and active editor data from https://commons.wikimedia.org/wiki/File:December_2020_Wikimedia_movement_metrics.pdf 

[4] December 2015 pageview data from https://stats.wikimedia.org/EN/TablesPageViewsMonthlyAllProjectsOriginal.htm

[5] December 2015 active editor data from an internal query across all Wikimedia sites, showing 79,420 active editors