The blog post about the community roadmap 2020Q1 includes a paragraph about increasing community engagement:
Though our active user base continues to grow, our engagement has remained the same. What this means is that while more users are coming to the site every month, the number of users who engage meaningfully in the site does not increase proportionally.
And Adam Lear subsequently commented:
There are a few different levels of engagement we look at (e.g. voting vs posting) and they feed into different things.
How does SE Inc. understand and define meaningful user engagement? Posting a question or answer is probably included, but what if the question or answer receives a negative score, is it still included? Are visits without asking anything or voting included?
The number of visits is increasing, probably even faster than the number of active users.
Which of these meaningful engagements particularly do not increase proportionally with the size of the active user base? What are the different levels of engagement, the company is looking at?
Why is SE wanting to increase engagement on SO? asks why the engagement should be increased. Here I only want to know how SE defines meaningful engagement and at what particular quantities they are looking at. This is not a discussion with other users even though it's tagged as one because of the required tags, I'm directly asking the company.