There are some really good questions being asked here.
However I'm noticing that a lot of questions don't have answers, or only have one answer.
How can we attract more expert users here?
I tend not to agree with the OP. Experts would be lured in by other experts (but here we have the "chicken-or-egg" issue), or by graduate-students-level questions -questions that are advanced and sophisticated enough, and closer to scientific papers and issues and actual research, so that they would trigger the interest of experts, mixed with a teaching desire (if any).
And this subset of questions, graduate-level ones, is the one we lack the most: We mostly have people trying to understand the economics of their life or society (essentially asking questions that are inherently very complex, and so very difficult to answer scientifically in a Q&A site), or undergraduate students asking mostly trivial theoretical questions.
What needs to be "targeted" is Master students and comparable.