The Times has a discussion about tenure in today's paper. Nothing really stands out in the discussion pieces, but one thing in the introduction did surprise me:

In 1975, 57 percent of all college professors had tenure or were on a tenure track. In 2007, that number had fallen to 31 percent, and a new federal report, to be released in the fall, is expected to show another decline for 2009, The Chronicle of Higher Education reported this month.

Think about that: fewer than all 1/3 of professors are tenured or tenure-track. And that's all professors. Given the much higher prevalence of tenure 30 years ago, that probably means that the tenure rate is considerably higher for older faculty members and much lower for new faculty members. Differences in attrition rates (untenured people are less likely to persist, I would think) likely further skew things.

If we assume that tenure/tenure-track rates for the faculty overall have fallen by about 1% per year and that rates for new faculty have also fallen by 1% per year, then from a back of the envelope calculation with some simplifying assumptions, one finds that tenure/tenure-track rates for new faculty are now closer to 15%. Wow.