There's some interesting data here about employment for PhDs since 1991. The article is mostly about the job market bust for PhDs in the sciences, and the data is compiled by NSF, but it includes employment data for PhDs in the Humanities. To sum up, employment rates in the Humanities were pretty much flat, hovering in the high 50s percentage-wise, until 2006, when a steady decline began. Academic employment went down and, correspondingly, unemployment went up. Both figures are now in the 40s. That was before the economic meltdown of 2008, so we're obviously seeing more at work than that particular disaster. In the same timeframe, postdocs have inched up, which jibes with my intuition on postdocs in philosophy. Seems like a lot of the new hires on Leiter's thread this year are postdocs.
Meanwhile, for PhDs overall, the decline actually began at the turn of the century, suggesting things might be somewhat worse in other disciplines. (Although people in the sciences have more opportunities to work in industry, and the data shows they are well-compensated for that work -- much better than Humanties PhDs who end up in the private sector.)
So, I guess the bad news is that the downward trend is unlikely to get better, even if the economy picks up, unless something else changes. The good news is it's not actually a lot worse than it used to be?