As elgilito demonstrated in July of 2015, there has been a long-term declining trend in user engagement ever since the great Google algorithm change of November 2012. This trend includes reductions in the number of posts, comments and active users on the blue. In one respect the politics megathreads have reversed this trend, as 2016 represents the first period of increasing comment volume since then.However, when we bucket the comments into whether they occurred in a US politics megathread or not (see below for my methodology in defining of a megathread), a more striking pattern emerges: the increase has been entirely due to comments in megathreads, and comment volume in other posts has decreased dramatically. During the period from July of 2016 through February 2017, politics megathreads actually have more comments than all other posts combined, an average of 713 comments a day within megaposts and 702 a day in all other threads.If we define July 2016 forward as the era of megathread dominance, the average number of posts to the blue has dropped immediately from the start of the era and continued to decline, from an average of 24 a day in the period of Nov. 2015 - Jun. 2016 to an average 17.7 a day during Jul. 2016 - Feb. 2017. Monthlong posting campaigns such as #julybywomen, #womensmarch and #keepmefiweird had the opposite effect of increasing post volume, but largely created one-off effects that did not reverse long-term declines.The decline in volume of users commenting each month has also been a long-term trend throughout the post-Google-algorithm-change era, and has also accelerated during the megathread era, although not as dramatically as post volume. Notable is that, while the volume of comments within and outside US politics megaposts has been roughly equal during the megathread era, only a minority of participating users comment drive those comments. In any given month during the megathread era, two thirds of active commenters that month never commented in a megathread.While the posts by women months and keepmefiweird all drove more posts being created, the posts by women months also correlated with more users participating in conversation, which keepmefiweird did not.To preserve the long term viability of the blue, the moderators and the userbase at large should consider policies and behaviors that could curtail the growth of the megathreads and encourage participation on a broader variety of topics by a wider set of users.Monthly posting campaigns have been effective in the short term, but we need to do more than that if we want to see long-term increases in the breadth and diversity of the engaged user base and topics of conversation on the blue.The analysis was based on queries against the tagdata_mefi, commentdata_mefi and postdata_mefi tables from the infodump, meaning that the only subsite in scope is the blue. The period reviewed is 1/1/2013 through 2/28/2017.For the purposes of this analysis, a thread was considered a US politics megathread if it had 500 or more comments and was tagged with at least one of the following: election2016 election potus45 DonaldTrump BarackObama obama trump hillaryclinton BernieSanders Clinton sanders USPolitics