Re:Netflix Spilled Your Brokeback Mountain Secret, Lawsuit C...
by gojomo on Friday December 18, 2009 @03:44AM
(#1002812)
Back of the envelope:
~300 million Americans spread among ~100,000 zip codes yields an average of 3,000 people per zip code. So zip code alone narrows a person down to a set of around 3,000. Gender then to 1,500.
That's only 4.2 years worth of unique birthdays! Unless the zip code is dominated by a certain age group (as around a college campus), there should be a lot of unique birthdays, since those will be drawn from a range of many decades.
Do densely-packed cities change things much? A bit, but they probably also have helpful age-diversity. San Francisco has 800,000 people and 25 zip codes -- 32,000 per zip code; 16,000 per gender; 16,000 unique birthdays would cover 45.2 years.
So there are sure to be more collisions, but still many unique zip/sex/DOB combinations. And for all the zip codes with < 3,000 residents, the people uniquely addressable could be 97, 98, 99%.
If we take zip+4, it's all over. My 12-unit apartment building has 2 zip+4 codes all by itself, so zip+4 identifies a group of < 12 people.
~300 million Americans spread among ~100,000 zip codes yields an average of 3,000 people per zip code. So zip code alone narrows a person down to a set of around 3,000. Gender then to 1,500.
That's only 4.2 years worth of unique birthdays! Unless the zip code is dominated by a certain age group (as around a college campus), there should be a lot of unique birthdays, since those will be drawn from a range of many decades.
Do densely-packed cities change things much? A bit, but they probably also have helpful age-diversity. San Francisco has 800,000 people and 25 zip codes -- 32,000 per zip code; 16,000 per gender; 16,000 unique birthdays would cover 45.2 years.
So there are sure to be more collisions, but still many unique zip/sex/DOB combinations. And for all the zip codes with < 3,000 residents, the people uniquely addressable could be 97, 98, 99%.
If we take zip+4, it's all over. My 12-unit apartment building has 2 zip+4 codes all by itself, so zip+4 identifies a group of < 12 people.