9 ms·

ZIP codes are an emergent property of the mail delivery system. While the author might consider this a bad thing, this makes them "good enough" on multiple axes

ZIP codes are an emergent property of the mail delivery system. While the author might consider this a bad thing, this makes them "good enough" on multiple axes in practice. They tend to be: - Well-known (everybody knows their zip code) - Easily extracted (they're part of every address, no geocoding required) - Uniform-enough (not perfect, but in most cases close) - Granular-enough - Contiguous-enough by travel time Notably, the alternatives the author proposes all fail on one or more of these: - Census units: almost nobody knows what census tract they live in, and it can be non-trivial to map from address to tract - Spatial cells: uneven distribution of population, and arbitrary division of space (boundaries pass right through buildings), and definitely nobody knows what S2 or H3 cell they live in. - Address: this option doesn't even make sense. Yes, you can geocode addresses, but you still need to aggregate by something.

mattforrest 2y ago
Well you hit on all the points that discuss the compromises that zip codes offer. Just because you have them in your data doesn't mean that they can produce anything useful. You are correct that no one knows their census unit is (if you are thinking from someone entering this on a website) but collecting location or address will be a lot better. Fact is a lot of web data contains a zip but if you can collect something better it will usually render better results. Unless you are analyzing shipments then that is fine.
ellisv 2y ago
There are point process models, but, yes, its much more common to want to aggregate to a spatial area. Another consideration is what kind of reference information is available at different spatial units. There are plenty of Census Bureau data available by ZCTA but some data may only be available at other aggregate units. Zip Codes are often used as political boundaries. I'd also mention the "best" areal unit depends on the data. There is a well known phenomenon called the modifiable areal unit problem in which spatial effects appear and vanish at different spatial resolutions. It can sort of be thought of as a spatial variation of the ecological fallacy.
ericrallen 2y ago
This is a tangent, but addresses are also way more complicated than most people realize - especially if you’re relying on a user to input a correct address or if you need to support multiple countries, somewhere with unique addresses like Queens[0], or you need to differentiate between units of a specific street address that uses something other than unit numbers for a unit designation. At that point you need something like Smarty[1] to validate and parse addresses. [0]: https://stackoverflow.com/questions/2783155/how-to-distinguish-a-ny-queens-style-street-address-from-a-ranged-address-and https://stackoverflow.com/questions/2783155/how-to-distingui... [1]: https://www.smarty.com/ https://www.smarty.com/
- nitwit005 2y ago
  Yes, unfortunately, their assertion that everyone knows their zip code is wrong. People often write a neighboring code, and the post office just delivers it. Similar issues for city name, of course.
  - VWWHFSfQ 2y ago
    Very common in NYC. People will use all of "New York, NY", "Queens, NY", or "Astoria, NY" all interchangeably and the post office will still just deliver it to the same place.
    - ericrallen 2y ago
      This is sort of apocryphal - and also anecdotal because I have my own personal experience living in an annexed Boston neighborhood to draw on - but in a lot of the towns/neighborhoods that have been annexed by Boston, people still use the neighborhood name[1] as the city name because you are more likely to get your package when you indicate which “Washington St,” “Boylston St,” etc. you actually live at. According to one commenter on the subject: It doesn't matter, as long as the zip code is correct [0]: https://www.city-data.com/forum/boston/601106-mailing-address-jp-dorchester-etc.html https://www.city-data.com/forum/boston/601106-mailing-addres... [1]: https://www.city-data.com/forum/boston/601106-mailing-address-jp-dorchester-etc.html https://www.city-data.com/forum/boston/601106-mailing-addres...
o11c 2y ago
Also, "use a different grid" is only masking the problem, not actually fixing it. The real problem is ever using an average without also specifying some sort of bounds. For median-based data, this probably means the upper and lower quartiles (or possibly other percentiles); for mean-based data, this probably means standard deviation.
JumpCrisscross 2y ago
Would add that there are network effects with zip code data. If you collect H2 data, you have fewer sources with which to join.
walrus01 2y ago
In terms of "good enough", a Canadian postal code, broadly equivalent to a zip code, is much more granular and can often identify an individual apartment building, or single city block. Plenty of large office buildings in major Canadian cities also have their own postal code. The functionality of it is closer to the "Zip+4" with extension used to have a more granular routing of physical mail for USPS. https://www.canadapost-postescanada.ca/cpc/en/support/articles/addressing-guidelines/postal-codes.page https://www.canadapost-postescanada.ca/cpc/en/support/articl... https://en.wikipedia.org/wiki/Postal_codes_in_Canada https://en.wikipedia.org/wiki/Postal_codes_in_Canada
- ssl-3 2y ago
  Sure, and in the States, ZIP+4 could once nail my postal location to a subset of 4 (of a group of 16) mailboxes within a particular set of entry doors on a particular apartment building. But broadly speaking, nobody knows what their ZIP+4 is, while I imagine that most people in Canada know their postal code by heart. It is interesting.
  - bluGill 2y ago
    The plus four changes all the time so it isn't feasable to know it. The use is large mailers can get a discount by looking it up and presorting mail. If the mail coming into my post office has my mail next to my next door neighbors that saves them a lot of time.
    - kstrauser 2y ago
      Is that still true? I would imagine any reasonably modern computer could map every physical address in a huge region to a (route number, stop number) pair. I wouldn't think the +4 would add a lot of value anymore.
      - bluGill 2y ago
        The sort everything outgoing by where it goes on the truck is valuable. sure computers can sort but this is physical things and so mechanical limits apply.
hinkley 2y ago
Contiguous enough by data travel time as well. A few people will get 5 ms more latency than the exact optimal route, but it’s not like your routes are exactly optimal anyway. And don’t forget sales tax. Which is state + county + city
- kstrauser 2y ago
  ... + special entertainment district + business renovation area + exception + exception + exception + ...
michaelmrose 2y ago
If you are worrying about address at all instead of tax or legal jurisdiction its probable that you as a business have a physical presence. You can probably correlate better by predicting which location a given address would likely interact with if you don't know already by prior purchases/interaction which they normally do so. I would suggest actual purchase data followed by travel time. Zip and distance as the crow flies often gives shit data. My zip suggests I'm off in bum fuck and since I'm on the puget sound things that are relatively near as the crow flies can actually be hours away.
killjoywashere 2y ago
ZIPs are also specifically used in a variety of medical, epidemiologic, public health contexts and HHS has explicit, fairly fine-grained rules on their use: https://www.hhs.gov/hipaa/for-professionals/special-topics/de-identification/index.html#zip https://www.hhs.gov/hipaa/for-professionals/special-topics/d...
raphman 2y ago
One more advantage: ZIP codes are a good trade-off if you want to gather anonymous data in a survey or provide anonymized data to an outside entity. For example, we recently conducted a survey on mobility patterns within our university. To offer respondents a reasonable amount of anonymity, we just asked for their (German) ZIP code and the location of their primary workplace. This allows us to determine the distance and approximate route people would take between home and university campus - to a degree that is sufficient for our goals.
stevage 2y ago
> Easily extracted (they're part of every address, no geocoding required) That's only true if you can also access the spatial boundaries of the zipcodes themselves. In Australia, this turns out not to be true: the postal system considers their boundaries to be commercial confidential information and doesn't share them. The best we can do is the Australian Bureau of Statistics' approximations of them, which they dub "postal areas".
MathCodeLove 2y ago
On the note of census units, the only reason we all know our zipcode is because we have to know it. If census units were used as frequently as zip’s I imagine they would quickly become more widely known as well.

mattforrest 2y ago

Well you hit on all the points that discuss the compromises that zip codes offer. Just because you have them in your data doesn't mean that they can produce anything useful. You are correct that no one knows their census unit is (if you are thinking from someone entering this on a website) but collecting location or address will be a lot better. Fact is a lot of web data contains a zip but if you can collect something better it will usually render better results. Unless you are analyzing shipments then that is fine.

ellisv 2y ago

There are point process models, but, yes, its much more common to want to aggregate to a spatial area. Another consideration is what kind of reference information is available at different spatial units. There are plenty of Census Bureau data available by ZCTA but some data may only be available at other aggregate units. Zip Codes are often used as political boundaries. I'd also mention the "best" areal unit depends on the data. There is a well known phenomenon called the modifiable areal unit problem in which spatial effects appear and vanish at different spatial resolutions. It can sort of be thought of as a spatial variation of the ecological fallacy.

ericrallen 2y ago

This is a tangent, but addresses are also way more complicated than most people realize - especially if you’re relying on a user to input a correct address or if you need to support multiple countries, somewhere with unique addresses like Queens[0], or you need to differentiate between units of a specific street address that uses something other than unit numbers for a unit designation. At that point you need something like Smarty[1] to validate and parse addresses. [0]: https://stackoverflow.com/questions/2783155/how-to-distinguish-a-ny-queens-style-street-address-from-a-ranged-address-and https://stackoverflow.com/questions/2783155/how-to-distingui... [1]: https://www.smarty.com/ https://www.smarty.com/

nitwit005 2y ago
Yes, unfortunately, their assertion that everyone knows their zip code is wrong. People often write a neighboring code, and the post office just delivers it. Similar issues for city name, of course.
- VWWHFSfQ 2y ago
  Very common in NYC. People will use all of "New York, NY", "Queens, NY", or "Astoria, NY" all interchangeably and the post office will still just deliver it to the same place.
  - ericrallen 2y ago
    This is sort of apocryphal - and also anecdotal because I have my own personal experience living in an annexed Boston neighborhood to draw on - but in a lot of the towns/neighborhoods that have been annexed by Boston, people still use the neighborhood name[1] as the city name because you are more likely to get your package when you indicate which “Washington St,” “Boylston St,” etc. you actually live at. According to one commenter on the subject: It doesn't matter, as long as the zip code is correct [0]: https://www.city-data.com/forum/boston/601106-mailing-address-jp-dorchester-etc.html https://www.city-data.com/forum/boston/601106-mailing-addres... [1]: https://www.city-data.com/forum/boston/601106-mailing-address-jp-dorchester-etc.html https://www.city-data.com/forum/boston/601106-mailing-addres...

o11c 2y ago

Also, "use a different grid" is only masking the problem, not actually fixing it. The real problem is ever using an average without also specifying some sort of bounds. For median-based data, this probably means the upper and lower quartiles (or possibly other percentiles); for mean-based data, this probably means standard deviation.

JumpCrisscross 2y ago

Would add that there are network effects with zip code data. If you collect H2 data, you have fewer sources with which to join.

walrus01 2y ago

In terms of "good enough", a Canadian postal code, broadly equivalent to a zip code, is much more granular and can often identify an individual apartment building, or single city block. Plenty of large office buildings in major Canadian cities also have their own postal code. The functionality of it is closer to the "Zip+4" with extension used to have a more granular routing of physical mail for USPS. https://www.canadapost-postescanada.ca/cpc/en/support/articles/addressing-guidelines/postal-codes.page https://www.canadapost-postescanada.ca/cpc/en/support/articl... https://en.wikipedia.org/wiki/Postal_codes_in_Canada https://en.wikipedia.org/wiki/Postal_codes_in_Canada

ssl-3 2y ago
Sure, and in the States, ZIP+4 could once nail my postal location to a subset of 4 (of a group of 16) mailboxes within a particular set of entry doors on a particular apartment building. But broadly speaking, nobody knows what their ZIP+4 is, while I imagine that most people in Canada know their postal code by heart. It is interesting.
- bluGill 2y ago
  The plus four changes all the time so it isn't feasable to know it. The use is large mailers can get a discount by looking it up and presorting mail. If the mail coming into my post office has my mail next to my next door neighbors that saves them a lot of time.
  - kstrauser 2y ago
    Is that still true? I would imagine any reasonably modern computer could map every physical address in a huge region to a (route number, stop number) pair. I wouldn't think the +4 would add a lot of value anymore.
    - bluGill 2y ago
      The sort everything outgoing by where it goes on the truck is valuable. sure computers can sort but this is physical things and so mechanical limits apply.

hinkley 2y ago

Contiguous enough by data travel time as well. A few people will get 5 ms more latency than the exact optimal route, but it’s not like your routes are exactly optimal anyway. And don’t forget sales tax. Which is state + county + city

kstrauser 2y ago
... + special entertainment district + business renovation area + exception + exception + exception + ...

michaelmrose 2y ago

If you are worrying about address at all instead of tax or legal jurisdiction its probable that you as a business have a physical presence. You can probably correlate better by predicting which location a given address would likely interact with if you don't know already by prior purchases/interaction which they normally do so. I would suggest actual purchase data followed by travel time. Zip and distance as the crow flies often gives shit data. My zip suggests I'm off in bum fuck and since I'm on the puget sound things that are relatively near as the crow flies can actually be hours away.

killjoywashere 2y ago

ZIPs are also specifically used in a variety of medical, epidemiologic, public health contexts and HHS has explicit, fairly fine-grained rules on their use: https://www.hhs.gov/hipaa/for-professionals/special-topics/de-identification/index.html#zip https://www.hhs.gov/hipaa/for-professionals/special-topics/d...

raphman 2y ago

One more advantage: ZIP codes are a good trade-off if you want to gather anonymous data in a survey or provide anonymized data to an outside entity. For example, we recently conducted a survey on mobility patterns within our university. To offer respondents a reasonable amount of anonymity, we just asked for their (German) ZIP code and the location of their primary workplace. This allows us to determine the distance and approximate route people would take between home and university campus - to a degree that is sufficient for our goals.

stevage 2y ago

> Easily extracted (they're part of every address, no geocoding required) That's only true if you can also access the spatial boundaries of the zipcodes themselves. In Australia, this turns out not to be true: the postal system considers their boundaries to be commercial confidential information and doesn't share them. The best we can do is the Australian Bureau of Statistics' approximations of them, which they dub "postal areas".

MathCodeLove 2y ago

On the note of census units, the only reason we all know our zipcode is because we have to know it. If census units were used as frequently as zip’s I imagine they would quickly become more widely known as well.