The Japanese Wikipedia is the second wikipedia in traffic ....

Sorry but I am missing the connection: aren't we asking about the desired ratio of contributors to readers? It seems like that's something we can discuss independently of article counts or whatever.

A ratio is a comparison to something else.. What ratio are we discussing. If this is not relevant, then fine.. It only means that the way the question was put is not appropriate. I think it is largely irrelevant, the question could have been "how do we grow our editor community in relation to the number of people visiting our wikis" this question at least acknowledges that only readers become editors ... the current question assumes that everyone knows about our projects.