PF's been running long enough to make some quantitative statements re. "participation." On the homepage you'll see total posts and total threads for each forum: for the science, math, and engineering you'll notice an average of 5 -10 posts per thread; for philosophy, GD, and P&WA you'll notice 20 -30 posts per thread. This isn't noticeably different from a year ago. Once you get into the individual fora you see "posts" and "views" for each thread. This ratio will give you a "hint" at participation, or interest, in the thread topics. Science, math, engineering run 30 - 100 views per post. Philosophy and P&WA run 10, maybe a little less. Again, no real change from year or two ago. Conclusion? There are small, very active groups of participants in philosophy, and in P&WA.