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 <https://wikimediafoundation.org/news/2021/02/04/wikimedia-foundation-ceo-katherine-maher-to-step-down-in-april-2021/> 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_me… [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 -- Kate Zimmerman (she/they) Director of Data Science, Product Analytics Wikimedia Foundation On Wed, Mar 17, 2021 at 1:56 AM Tilman Bayer &lt;haebwiki(a)gmail.com&gt; wrote:

Hi Federico, The data we have from active editors in 2015 is taken from a snapshot and uses the same filters and logic as the data for 2020. More about our definitions, as well as a link to the code we use to calculate the metrics, available here: https://www.mediawiki.org/wiki/Wikimedia_Product/Data_glossary#Editors Warm regards, Kate On Thu, Apr 29, 2021 at 11:31 PM Federico Leva (Nemo) &lt;nemowiki(a)gmail.com&gt; wrote: