> So there's a fairly constant fall-off of activity from people who've previously posted a lot. And this gets worse when these folks find fewer questions that interest them
As noted in the comments there, this tends to be slightly inaccurate, as it ignores changes in reputation over time. But it's close enough to see the general trend; I left a comment with a more accurate picture of the usual trend and the more recent drop-off.
Is this data publicly available?