TL;DR: never underestimate https://xkcd.com/214/ ? :) We must be careful NOT to provide users [only] what they are looking for.
Toby Negrin, 14/10/2015 07:43:
There's a strange artifact in the desktop page views where they drop by about 75mm at the end of 2013 but don't recover. Do we understand what happened here.
Irrecoverable effects of One Direction album? ;) https://lists.wikimedia.org/pipermail/mobile-l/2013-December/006342.html
In that period there was a lot of work around redirects and forcing users to use the mobile site. One major forceful redirect was in June 2014 (tablets) and you clearly see the impact on Jon's graphs.
SAL and https://www.mediawiki.org/wiki/Extension:MobileFrontend/Deployments are not particularly useful for historical digging, it would be great to have a timeline of major mobile configuration changes (or at least of redirects). http://bugs.wmflabs.org/buglist.cgi?chfield=resolution&chfieldfrom=2013-... finds e.g. http://bugs.wmflabs.org/show_bug.cgi?id=57127 and http://bugs.wmflabs.org/show_bug.cgi?id=49653
Things worth testing (or data worth recovering from the past if possible) for their effect on session length: * collapsing sections by default, providing easy "expand all" features etc.; * collapsing/hiding other content (and maybe interface elements too); * forceful redirects by device (e.g. did the forceful redirect for tablets increase session length on tablets?); * other major alterations AKA hacks compared to desktop.
Then the specific subcases can be switched to the experience which proved most immersive.
Nemo