Depending on how you define interview. In my experience a rough funnel of 100 people (random people through a job board, not referrals) -> 20 phone screens -> 5-10 actual interviews. Generally at large organizations in the Valley a rate of 10 on campus interviews to one offer is considered inefficient (shoot for ~5 from an efficiency perspective). Too many in person interviews generally suggests a weak filter in an earlier step (you can learn quite a bit from a phone screen, for instance).