Well, there are 366 dates of birth, and 9999 last 4 digits in SSNs, so approxima...

		Dove on Aug 2, 2013 \| parent \| context \| favorite \| on: We have an employee whose last name is Null. He ki... Well, there are 366 dates of birth, and 9999 last 4 digits in SSNs, so approximately 3.7M combinations. If you drop 380k users into 3.7M buckets, that's only ten times as many buckets as users. A lot of the buckets will be shared.