Dr. Michael Pelczar from the Department of Philosophy at the National University of Singapore writes:

The thread in your site on publication and hiring prompted me to do some informal fact finding. I thought that there might be some interest in the results.

I visited the websites of the top 50 U.S. philosophy programs as reported in the latest (2004-06) edition of the Gourmet Report, and identified all the faculty members of these departments who received their PhDs in 1999 or since. There are 108 of these, by my count. (I may have missed a few, since in a handful of cases it wasn’t clear when the degree was conferred.) For each faculty member, I looked up the Gourmet Report ranking of his or her PhD program at the time that he or she graduated, and for the two years prior to that. (I treated Oxford and ANU as top ten programs.) Of 108 individuals, 81 graduated from top 10 departments, 97 from top 20 departments, 103 from top 30 departments, and 106 from ranked departments. So:

Top 10:  75%
Top 20:  90%
Top 30:  95%
Ranked: 98%

I don’t draw any conclusions from these numbers, besides the obvious one that ranked departments have a strong preference for junior candidates from top 20 programs.

Remember, of course, that categories like "top 10" and "top 20" may include slightly more than 10 or 20 faculties, because of ties.