[mooism2]

If you have connections, you can land the job before it is advertised publicly; therefore the job won't be advertised publicly.

If you don't have connections, you can't land a job that isn't advertised publicly.

Publicly advertising a job is tedious.

[BadCode]

That makes sense. Considering the resources required to shortlist candidates and interview them, companies would any day prefer to avoid it. Is there any relevant data, how many such jobs may exist that are not 'advertised'?

[mooism2]

There is relevant data, but I don't know where it is, sorry.

I am under the impression that this sort of under-the-radar hiring occurs enough to be a significant cause of institutional racism in hiring. (If your existing employees are disproportionately white, and their friends and acquaintances are disproportionately white, then new employees who fill a position before it is publicly advertised will be disproportionately white; and this is without anyone being overtly or consciously racist, and without non-whites being discouraged in any way from applying.)