It is clear signal but its causes are multiple and I am not sure what percent attribution each one has:

1) Roles with high turnover. Likely the posting stays always on. 2) The pay is bad and nobody takes the job. 3) The role is too niche and the candidates in the market with visibility to the role are very few. 4) Aggressive hiring. Candidates have many options and until they actually show up at work, you keep interviewing other candidates. 5) Forgotten posts / ghost posts (my gut feeling says that this is the lowest contributor to the spike we observe, as likely it should be flat over time)

Reposts from recruiting agencies or other unrelated companies to resell the candidates or simply farm user details for fraud etc.

So, you’re saying it’s not really a clear signal?