Might be offtopic, but again maybe not. In any case this is not really answering the question, just some additional information (seemingly) related. I've rerun the query [about total questions and answers together](http://data.stackexchange.com/mathoverflow/query/482464/total-questions-and-answers-per-month-for-the-last-120) for the period indicated (could not run it for longer time stretch). What I've got is this:

[![enter image description here][1]][1]

Seems like for the first time in 2016 the total number of questions has exceeded the total number of answers.

I believe one might conclude that the number of questions actually grows, although more slowly than the number of answers drops.

And here is an update for 2015 - 2017. I believe it rather confirms than contradicts the suggestion that there is a tendency for a combination of an upward trend in questions and downward trend in answers...

[![enter image description here][2]][2]


  [1]: https://i.sstatic.net/nTRpN.png
  [2]: https://i.sstatic.net/elqtu.png