[Talk-us] Correct source for population=* tags on US metropolitan cities

[Joseph Eisenberg]

Proposal:
Use the census data on Urbanized Areas to set the "population=" value for
"place=city" nodes, rather than using the whole metro population or just
the population of the central municipality.

Rationale:
The tag "population=*" is helpful as a way to distinguish small place=city
features (which might have less than 50,000 people in rural States) from
huge cities. Many database users depend on this information for rendering
decisions at low zoom levels (large scales) and as a general estimation of
the "importance" of a place.

However, currently most population figures are taken from the population in
the municipal boundaries, since this is often what is on local signs and
easily available from the census. While this is fine for towns and small
cities which are contained in one municipality, it often misses
unincorporated urban areas next to the city limits, and for large cities it
badly underestimates the population of the area which is considered part of
the "place".

For example, many people in West Hollywood or East Los Angeles would
consider that they live in the larger place "Los Angeles", even though they
live in a different municipality or an unincorporated area. Someone who
lives in Vancouver, Washington will often tell people they live "In
Portland" when talking to someone from outside of the region, since it
functions as a suburb of the Portland, Oregon metro area.

So I propose that we should use an estimate of the urban population for the
population=* tag when tagging metropolitan places. Usually this will lead
to a larger population number, except in rare cases like Anchorage.

In particular, I would like to use the US Census "urbanized area" figures,
since these are much more sensible than the numbers from metropolitan areas
based on county boundaries which can include distant towns and rural areas.

This would mean that the place=city node for Portland, Oregon would have
population=2072553 (representing the whole urbanized area) rather than just
654000 from the city limits.
https://censusreporter.org/profiles/40000US71317-portland-or-wa-urbanized-area/

Minneapolis, MN would have population=2885614 instead of only 429k
https://censusreporter.org/profiles/40000US57628-minneapolis-st-paul-mn-wi-urbanized-area/


But Anchorage would decrease slightly from 288k to 249K
https://censusreporter.org/profiles/40000US02305-anchorage-ak-urbanized-area/

Usually the difference would not change the relative rank of cities very
much, but it would be good to have the population figure map the
OpenStreetMap "place" concept, rather than the city limit boundaries.

Eventually this could improve maps of the USA and help them better match
those in other countries, where city limits tend to be much larger than in
the case of many US cities, which often have many separate municipalities
for suburbs.

Of course it will still be appropriate to add the precise population=* to
the boundary=administrative feature which represents the municipality, and
database users could choose to emphasize those features instead.

-- Joseph Eisenberg

PS: the 2010 population figures of US Urbanized Areas are on wikipedia, and
this year we will get updated 2020 figures, so it would be a good time to
make this change. The biggest difference will be for Miami, Florida, where
the central municipality is only 7% of the population of the whole
urbanized area:
https://en.wikipedia.org/wiki/List_of_United_States_urban_areas
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