We all know about the oversupply problem in academic science wherein we are minting new PhDs faster than we create / open faculty jobs to house them.
Opinions vary on what is the proper ratio. All the way from "every PHD that wants a hard-money traditional Professorial job should get one" to "who cares if it is 1% or even 0.001%, we're getting the best through extreme competition!"
(I fall in between there. Somewhere.)
How would we detect it, however, if we've made things so dismal that too many trainees are exiting before even competing for a job?
One way might be if a job opportunity received very few qualified applicants.
Another way might be if a flurry of postdoctoral solicitations in your subfield appeared. I think that harder flogging of the advert space suggests a decline in filling slots via the usual non-public recruiting mechanisms.
I am hearing / seeing both of these things.