* Institution type: Professors at elite private universities might skew older than those at community colleges.
* Field of study: Some fields might have more early career professors (e.g., computer science) while others might have a higher proportion of older professors (e.g., history, philosophy).
* Rank: Full professors are generally older than assistant or associate professors.
* Country: Age distributions will vary across nations.
While precise statistics are hard to come by, a reasonable estimate would place the average age somewhere in the late 40s to mid-50s. However, this is a broad generalization, and the actual average could be higher or lower depending on the specific factors mentioned above.