How relevant retired postcodes are to the use of the addresses we find in Land Registry’s Price Paid (LRPP) data?
First of all, what do we call “active” postcodes? As Ordnance Survey’s open data is central to OLAF, let’s use OS’ view of the world.
There are 1,510,219 postcodes in England and Wales according to Ordnance Survey’s “Open Names” (OSON). I presume OSON describes live data only, so all these postcodes are presumed active. Note that I’m limiting my investigation to England and Wales as Land Registry just gives me data for those two countries.
Just to be sure, I check the same against another source: the Office for National Statistics’ “Postcode Directory” (ONSPD) data. I get 747,213 active postcodes there, over a total of 2,277,165 historically.
I can’t explain the discrepacy for the time being. My working assumption going forward is that the postcodes I find in OSON is a mix of current and recently retired postcodes.
Then, let’s see a) how many postcodes in LRPP are not in OSON and b) how many LRPP entries are affected. I get the first by doing:
The answer to (a) is 606,793, while…
… (b) is 10,697,707 , that is more than half of all LRPP!
So, the answer is that retired postcodes are very relevant to the use of LRPP.
Relevant, how? That’s for another blog post.