More broadly it would be good to know if wikiprojects are good for editor recruitment and retention. My hypothesis is that if someone if someone tries out editing Wikipedia and is steered to an active and relevant wikiproject then they will be more likely to continue after that first trial edit. I simply don't know whether introducing people to inactive wikiprojects is worthwhile or what the cutoff is on activity.

we could have a phenomenon here that will over time exacerbate wikipedia's problem of patchy coverage with the better covered topics improving faster than the gaps. Conversely if each topic has a founder effect then over time Wikipedia will become less uneven as more and more topics go through the phase of having an active editor or editors making their mark on the topic by radically improving articles.