[Peroni]

>One thing that could be very useful is a website tracking job postings and their close dates.

Not convinced this will be useful to you. Most job boards have a default display period (typically 30 days) and it's rare that a job will be closed manually within that timeframe. Job posts on careers pages are likely to be more accurate but the data is going to be extremely tricky as a lot of career page content tends to be catch-all content to ensure an 'always on' pipeline of candidates and the teams that manage these career pages aren't always efficient at closing roles once they've been filled.