American colleges and universities simultaneously face large numbers of faculty retirements and expanding enrollments. Budget constraints have led colleges and universities to substitute part-time and full-time non-tenure-track faculty for tenure-track faculty, and the demand for faculty members will likely be high in the decade ahead.

This heightened demand is coming at a time when the share of American college graduates who go on for PhD study is far below its historic high. The declining interest of American students in doctoral programs is due to many factors, including long...