How successful are the people you hire, and how well do you avoid bad hires? Ultimately, until you have a few years of data on your own decisions, it's hard to know how "effective" your interviewing process was. And even then, without wider baselines for comparisons within your corporation, you don't know how much better you could have done -- you only know how poorly you did by how many people you either had to terminate or did not turn into the high performers you expected.

Most big tech companies probably do this -- if you had done a few years of hiring at Google, I'd bet recruiting could have told you how you did. At Microsoft, recruiting could tell you where your recommendations ended up, how you ranked as an interviewer, etc.

The week on-site is probably a good substitute if you don't already have someone on your team with the proven ability to asses talent and fit rigorously and quickly.