From Labor online (LAWCHA), article by Trevor Griffey.
"Contrary to what most journalists and many academics argue, an “oversupply” of people with PhDs is not the primary cause of the decline of tenure for college faculty in the U.S."
His conclusion is of interest to all adjuncts:
"Most tenure track faculty want to convert adjunct lines to tenure track lines using open searches. This approach would restore tenure in schools across the country, to the benefit of recent recipients of PhDs, and at the expense of current adjunct and graduate student instructors. Most non-tenure track instructors, however, want to promote adjunct faculty to tenure track positions without open searches, based on seniority."