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87% of the U.S. Population are uniquely identified by {DOB, gender, zip}

latanyasweeney.org

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Re: 87% of the U.S. Population are uniquely identified by {DOB, gender, zip}

#2
While I find this fascinating, I'm sure this is old news to people in the business, like the people that run the grocery/chain store savings programs.

What I'd be really interested to see is why this works, and what it tells us about distribution of population by zip code. I'd imagine the places where this doesn't work as well, are the most densely populated zip codes, where the likely hood of duplicates on the given key increases, but I would never have guessed that the accuracy would be anywhere near 87%. (maybe there's alot more zipcodes than what I thought? maybe they used zip+4?)

Re: 87% of the U.S. Population are uniquely identified by {DOB, gender, zip}

#5
Here's some backstory, from the 1990s when the Massachusetts' Group Insurance Commission released "anonymized" health data:

''At the time GIC released the data, William Weld, then Governor of Massachusetts, assured the public that GIC had protected patient privacy by deleting identifiers. In response, then-graduate student Sweeney started hunting for the Governor’s hospital records in the GIC data. She knew that Governor Weld resided in Cambridge, Massachusetts, a city of 54,000 residents and seven ZIP codes. For twenty dollars, she purchased the complete voter rolls from the city of Cambridge, a database containing, among other things, the name, address, ZIP code, birth date, and sex of every voter. By combining this data with the GIC records, Sweeney found Governor Weld with ease. Only six people in Cambridge shared his birth date, only three of them men, and of them, only he lived in his ZIP code. In a theatrical flourish, Dr. Sweeney sent the Governor’s health records (which included diagnoses and prescriptions) to his office.''

Source: http://arstechnica.com/tech-policy/news/2009/09/your-secrets...

Re: 87% of the U.S. Population are uniquely identified by {DOB, gender, zip}

#6
post #2

While I find this fascinating, I'm sure this is old news to people in the business, like the people that run the grocery/chain store savings programs. What I'd be really interested to see is why this works, and what it tells us about distribution of population by zip code. I'd imagine the places where this doesn't work as well, are the most densely populated zip codes, where the likely hood of duplicates on the given…

Birth date is pretty granular as well. A quick trip to the interwebs gives about 11k-12k people born each day, or 6k of each gender. There are 100k possible ZIP codes. The birth dates aren't evenly distributed, but they're reasonably close. The ZIP codes probably have a lot of clumping, but in dense urban areas they usually start cutting the areas into smaller pieces. The long tail of ZIP codes is probably well-populated. Out of 6k boys and 6k girls that share a birth date, expecting 5k of each to happen to land a unique ZIP out of 100k sounds reasonable to me.
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