33 bits of entropy to narrow down to a single individual. ~28 in USA UID, Gender, Age group, Zipcode and City, plus of course your medication habits, is probab

33 bits of entropy to narrow down to a single individual. ~28 in USA UID, Gender, Age group, Zipcode and City, plus of course your medication habits, is probably enough to deanonymize with a reasonable amount of confidence. Say age group is one of 8, age+gender is 5 bits of entropy. City zip is ~8. So that's 15 bits left on a good day. Throw in any off-the-shelf targeted marketing data (usally worth 10-25 bits iirc) and you might as well use SSN as the patient ID.