I expected old job posts to be the dead ones. It was the opposite.
(What got me watching: I once got a rejection about 26 hours after applying, on a Sunday, and the job stayed up.)
So I followed about 100,000 open US job posts on companies' own career sites for two weeks. Here's what happened.
The job you just found is the one most likely to vanish.
36.5% of jobs posted in the past week were gone within two weeks. For jobs posted a month or more earlier, it was 15.7%. Most old posts stayed up.
Gone doesn't always mean gone.
18% of the jobs that came down came back as a new posting. Same company, same title, same place, usually the same day. If you applied to the old one, your application may be sitting on the old copy.
"Urgent" is just a word.
Jobs that say "urgent" or "immediate hire" are about as old as everything else: 34.6% have been up 60+ days, vs 38.4% of all open jobs.
When a company pulls a batch, watch your application.
At companies that took down 10+ jobs in a single day, 27.8% of their remaining jobs came down over the next 9 days. Everywhere else: 11.0%. That's about 2.5x. Sometimes they stopped hiring. Sometimes they reposted the whole board with new dates.
So what I'd do: apply in week one, don't skip a job just because it's old, and when a job you applied to vanishes, search the company's careers page for the same title.
What's the fastest a job you applied to disappeared? Or have you seen one come back with a new date?
How I measured: I re-read each employer's own career site every day (98% within a day). "Came down" means gone from that site. "Reposted" means the same company, title and location posted again, which is a best guess. Point 1: 15,118 new and 53,871 older jobs open Oct 13, checked through Oct 27. Point 2: 30,330 takedowns since tracking started Oct 12 (median time to repost 0 days, 75% within 1.7 days). Point 3: 1,829 "urgent" jobs in a snapshot of jobs open Oct 27. Point 4: jobs open Oct 18, checked through Oct 27, at companies that took down 10+ jobs in one day Oct 14 to 17 (7,449 of 26,833 vs 8,346 of 76,123). US only.