The following graph shows that changes in the number of senior (typically tenured) hires by philosophy departments with graduate programs over the past several years are roughly parallel to that of junior hires. (The graph uses a logarithmic scale to better show proportionality, and is missing data from 2018-19 at the junior level.)
Looking further back, Schwitzgebel observes, based on counting announcements of senior hires at Leiter Reports, that this year’s 27 senior hires “is comparable to several previous years: 2010-2011 had 28, 2014-2015 had 30, and 2015-2016 had 29.”
More details here.
Eric Schwitzgebel (UC Riverside) looked into the numbers of senior hires in philosophy made in recent years.