
How ZIP codes nearly masked the lead problem in Flint - maxerickson
https://theconversation.com/how-zip-codes-nearly-masked-the-lead-problem-in-flint-65626
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DrScump
"But unlike postal codes in other countries which represent small areas
suitable for in-depth geographic inquiry (Google “N6C 2B5” for a Canadian
example), ZIP codes are woefully unqualified as units of analysis."

First of all, don't Canadian zip codes have the exact same limitation? Postal
codes in general are designed for _the convenience of mail delivery_ and
nothing else. (For that matter, mailing address often misidentifies the actual
city of residence if one lives near a boundary and _always_ states a phony
city if one is in unincorporated territory.)

There are two methods I can think of immediately to drill down into better
detail. For one, zip codes are _nine_ digits now, and using all nine digits
(Zip+4) yields extremely narrow detail (generally no larger than the
destination's building; often, homes have their _own_ Zip+4. But that still
leaves the problem of matching address to political boundary.

For _that_ , there are many datasets that match street address to the
underlying _parcel_ , and knowing the parcel provides you with actual city (if
in incorporated territory), state political district(s), city political
district, Congressional district, etc. It's used by mailhouses for sending
political mailers to the correct jurisdiction all the time.

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maxerickson
I don't know what the Canadian system is, but the example points to it being
street/block level:

[https://www.google.com/search?num=20&q=postal+code+N6C+2B5](https://www.google.com/search?num=20&q=postal+code+N6C+2B5)

As far as I understand zip+4 is for a given sorting route, so it won't
necessarily have nice spatial properties. The USPS anyway considers zip codes
to be collections of addresses, so it's sketchy to use them as areas.

The problem with the parcel data sets is getting access to them in a coherent
format without spending money. I actually came across this link on a the
twitter feed of someone behind Openaddresses
([https://openaddresses.io/](https://openaddresses.io/) ). They often get
addresses from parcel data,
[https://usopendata.org/2016/06/07/parcels/](https://usopendata.org/2016/06/07/parcels/)
but don't restrict themselves to it.

