Folks keep quoting the percentage decline in the number of unique characters running keys between season 1 and 2 and pushing that off as logged participation. That stat was misrepresented on this thread DF season 2 M+ 4 million fewer keys run than DF season 1 - #124 by Fauxstrasza-stormrage (and was corrected within the thread), but keeps getting thrown around erroneously.
Good luck ever getting one of them to link where they got that stat.