I had the same question. If they truly have job ad & outcome data from 10,000 companies, I feel like they could build a lot more interesting things than a fancy word processor.

One thought I have of where it might come from is some other job sites list how many people applied for a particular job. If they scraped that information plus the job posting they could gather this type of data pretty quick.

But, if that's the case, then that's measuring the wrong thing. In many ways, a lot of applicants are an anti-signal. It means you're spending time sifting through a huge haystack searching for that 1 needle. Ideally, they have data on like, the 5 year performance review for the candidate hired or something like that which is why I said I have no idea how they would get such data.

That depends on what question you are trying to answer. To get a lot of people to apply is one metric. You seem more concerned with the quality of the applicants which is fair enough but it's implied yourcvio or human beeings will take care of that part. I could still see some use for this even if I wouldn't pay too much attention to the score itself.