From the most recent year in Doctor's degrees conferred by postsecondary institutions, by field of study: Selected years, 1970-71 through 2019-20 , if we exclude the “Health professions and related programs” (any health professional who might be addressed as “Doctor …”) and “Legal professions and studies” (lawyers), we get approximately 73,215 probable PhDs.
Postsecondary Teachers : Occupational Outlook Handbook: : U.S. Bureau of Labor Statistics suggests that there are approximately 1,276,900 post-secondary teachers now, with growth of 156,700 from 2020-2030. If 1/40 of the current ones retire per year, plus the projected job growth per year, we get 47,593 new hires per year. However, this is likely optimistic, since some of those are part time adjunct jobs. But that means that 73,215 per year is a large oversupply, particularly for the subset of job openings that are the more desirable ones (tenure-track).