CCing @Halfak who may have opinions on this.

When I think about this, I'm lost unless I have a good sense for what these measurements will be used for. All measurement proxies will have weaknesses and strengths, so we ought to pick the right ones depending on our purposes. So, I start trending towards building measures that correspond to intuitive properties as they tend to be robust in generally useful ways.

Thinking out loud:

If you are looking for a count of the exact number of people who are "involved" with the WikiProject, then I think we'll struggle because I want to know everyone who consumes a task list from the project pages. I wonder if looking at page views of the project pages will also be a good indicator of "involvement".

Topic-focused WikiProjects have a sort of governmental agency over the articles within their scope. General discussions tend to happen on the project pages (or are coordinated by project members). Thinking of anyone who is active in that topic area as a "constituent" seems useful. Whether you are involved in the project coordination or not, the decisions made by the WikiProject members will affect you.

Then there are those who show up and interact on the project pages. I expect these to be a mixture of roaming Wikipedians (who knows to make posts on WikiProject pages about their ideas/concerns regarding the topic/coverage/etc of articles) and regulars who tend to stick close to one or a small set of WikiProjects. We'd probably want some study here to see how Wikipedians tend to organize their WikiProject involvements so that we can draw intuitive measures of from the data.

Finally, there's WikiProject coordination work. Beyond participating in discussions, there are Wikipedians who take on the role of developing the portal, task lists, etc. They make sure the WikiProject continues to run and goes in a good direction. This is highly centralized role that I expect few Wikipedians to fill at a time. Again, it seems like we could formalize measurements of this activity.

Recommendation from @Sadads:

@Harej: I don't have a whole lot of time for volunteer time, but would love to figure out who is active in Novels articles, to encourage more collaboration. However, the current list includes way too many people, most of which aren't significantly contributing -- and doesn't give me many opportunities for strategically intervening. It would be great to have the editors broken into several groups "Recently new accounts", "limited contributions to area" (<600 or 700 bytes of change), "significant contributions to area" (>700 bytes of change), and high frequency contributors (more than 15 edits in scope). With these groups, I would be able to better sort those people in the project. The other option could be making a table with sum change in bytes and # of edits in area and # of articles modified, so that project coordinators could determine what the sort criteria are. There are certain editors that, if I could sort the edit activity quickly, would be immediately ruled out in my outreach -- so I am not spamming -- and let me prioritize people who significantly participate. You could make it even better by running those edits through ORES for some quality/significance assessment, but that not a priority, Sadads (talk) 04:15, 24 February 2016 (UTC)