I started and abandoned a little side project a while ago where I wanted to see which employers tended to have the exact same (or fuzzy-the-same) "Who's Hiring" post month after month. Goal would be to find some signal about which posts were actually resulting in hiring (in other words, the company didn't come back with the same posting) and which ones were just trawling for the same job month after month without act…
So, not sure this methodology identify quite what you're looking for.