Are these medical records Anonymised ?, (birthday problem variant)

[B0b-A]

Are these medical records Anonymised ?, (“birthday problem” variant)

Anonymised medical records are to be sold in the UK ... https://www.google.co.uk/search?q=sell+NHS+medical+records+harvest

Are these medical records truly Anonymised ?

If a person’s date of birth, (year-month-day) , postcode (zip code), and gender is known
what are the odds that data could identify a specific person ?.

At first glance it looks like there may be sufficient information to identify a specific individual,
by using databases like register-of-births and the electoral-register.

But the calculation involves something similar to the anti-intuitive “birthday problem”,
where a anonymity increases rapidly with the group size if you only knew someone's birthday, (not date-of-birth).

 

[willem2]

In the birthday problem, the odds that there is at least one duplicate birthday between any 2 persons are much higher than you might expect, but here you want to have a duplicate for everyone.

 

[B0b-A]

As security researcher Ross Anderson points out, there are typically only a few dozen addresses in a post-code, so with access to a birth date (that may come from sources outside of HSCIC) it is fairly easy to make a correct personal identification for about 98 percent of people (the exceptions are twins, students, soldiers and prisoners).

http://www.wired.co.uk/news/archive/2014-02/04/care-data-nhs-healthcare

 

[AlephZero]

All this is hypothetical unless you can identify a database which does actually contain the current address and date-of-birth of a large proportion of UK residents.

Neither of the OP's suggestions do that. The register of births only shows where people were born, not where they currently live. The electoral register does not show the date of birth, the only age-related data is whether people are eligible to vote and eligible for jury service, and even that limited information may not be on the public copy of the database.

The national insurance number (similar to the US social security number) database, owned by the UK taxation authorities, would cover a large proportion of the population, but not children or people who have never been (legally) employed - but again that information is not publicly available.

Not that facts are of much interest to conspiracy theorists, of course!

 

[B0b-A]

... The register of births only shows where people were born, not where they currently live. The electoral register does not show the date of birth ...

If you know the date-of-birth and their current postcode then cross-referencing the register-of-births with the electoral-register could tell the names of people born on that date who have the same name as people who live in that postcode.

[ Apparently about 2000 births per day in the UK, and a comparable number of people living in a particular postcode]