Amsterdam is the first city to host three European DrupalCons: 2005 (first DrupalCon ever), 2014 and 2019 (ongoing). How many community members attended all three of them?

We analyzed all user profiles published on drupal.org to find out this and much more.

The flow: Amsterdam to Amsterdam to Amsterdam

You can hover/tap on the chart to see details. Apparently, less than 200 people from the current DrupalCon Amsterdam had never been seen before at a DrupalCon in Amsterdam, and a huge amount of those seen in Amsterdam for the first time in 2014 did not return. But this may well be due to people not updating their profile, so this should be assessed again once everybody has had time to put their attendance on record.

Out of the (not so few, it seems; but beware of cheaters, see below) pioneers from 2005, about 75% never returned. But some were still attending in 2014, some skipped 2014 but are back this year, and three heroes attended all DrupalCons Amsterdam (watch for the almost invisible segment bottom right in the chart). Kudos to them! Here they are, together with other statistics about DrupalCon Amsterdam.

Extending to Europe: attendees through 15 years of DrupalCon in Europe

Amsterdam 2019 is the 15th DrupalCon held in Europe. What about extending the analysis above to cover the entire history of DrupalCon in Europe?

Here is the entire flow from 2005 to 2019. The representation is a bit overwhelming due to the very high number of combinations, but hovering or tapping will help you see what goes where.

You can explore your path through the European DrupalCons and check how many people made your same choice at each step. For example, 58 community members decided, like me, to go from Barcelona 2007 to Paris 2009 (skipping 2008) and 534 community members decided to go from Paris 2009 to Copenhagen 2010.

Can we assess the community growth associated to each conference?

Left: how many new people joined at each conference (first DrupalCon presence); right: how many people left after each conference (last DrupalCon presence). So, e.g., after the recent Barcelona, Dublin and Vienna we lost more people than the conference attracted; while after London, Prague, Paris and Munich the members we gained with the event were more than those we lost after the event. Again, it is likely that the Amsterdam 2005 figures are altered by cheaters as discussed in the final paragraph.

And here's the overall ranking as far as European DrupalCons are concerned.

In red Nuvole team members, just for a bit of company pride.

The fine print

• Only DrupalCons held in Europe are considered. Drupal Europe 2018 is considered to be the European DrupalCon for the year 2018.
• Data were obtained using the little-known but very handy Drupal.org API as explained in a session, more focused on community demographics, we gave at Drupal Europe 2018.
• Like most d.o profile data, attendance to Drupal events is manually entered by each user. There are obvious cases of missing information (Dries being a notable example) and of cheaters (many very recent accounts claim an unlikely number of attended events).
• Data were algorithmically sanitized to remove suspicious entries (e.g., accounts created last month that self-proclaimed presence at all DrupalCons ever held) as much as possible. This was done for the tables but not for the charts. If you are affected, please point out any errors in the comments.
• If you are in Amsterdam now but forgot to tick the checkbox - don't worry, we had forgotten about it too. Go edit your profile ("Drupal" tab) and we'll update this post with fresh numbers this weekend.