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I am using v12.2.0-Win7-x64.

CityData[Entity[
  "City", {"Shanghai", "Shanghai", "China"}], "Population"]

Quantity[14007000, "People"]

Entity["City", {"Shanghai", "Shanghai", "China"}]["Population"]

Quantity[24152700, "People"]

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Question

Am I using these correctly? Why is there (such) a difference? Thanks for your help as always.

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    $\begingroup$ Spot checking a few cities, I'm seeing that EntityValue consistently gives a higher population than CityData. Maybe CityData adheres strictly to some sort of city boundary and EntityValue corresponds to a more informal concept of "city" that extends to surrounding areas? $\endgroup$
    – lericr
    Sep 28, 2022 at 16:39
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    $\begingroup$ AdministrativeDivisionData[{"Shanghai", "China"}, "Population"] gives about 23 million, which is closer to but still less than EntityValue[Entity["City", {"Shanghai", "Shanghai", "China"}], "Population"] $\endgroup$
    – lericr
    Sep 28, 2022 at 16:43
  • $\begingroup$ For Entity["City", {"Shanghai", "Shanghai", "China"}], I searched if there were "Metro Area" / "Suburban" population properties etc. but that attempt was not successful. $\endgroup$
    – Syed
    Sep 28, 2022 at 16:52
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    $\begingroup$ "PopulationDensity" is the same for both methods. That seems weird given that total population differs. $\endgroup$
    – lericr
    Sep 28, 2022 at 17:32
  • $\begingroup$ I sort of expected for someone with expertise in the Entity system to weigh in here. Since no one has, does it seem worth reporting the issue to Wolfram? $\endgroup$
    – lericr
    Sep 28, 2022 at 18:11

1 Answer 1

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THIS IS AN EXTENDED COMMENT

$Version

(* "13.1.0 for Mac OS X x86 (64-bit) (June 16, 2022)" *)

Clear["Global`*"]

With[{city = Entity["City", {"Shanghai", "Shanghai", "China"}]},
 Column@{
   CityData[city, "Population"],
   city["Population"],
   city[EntityProperty["City", "Population"]]}]

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The different data values appear to represent data for different dates.

(pop = Table[{yr, 
     Entity["City", {"Shanghai", "Shanghai", "China"}][
      Dated["Population", yr]]}, {yr, 2000, 2021}]) // Grid

enter image description here

The older data appears to be either interpolated or extrapolated. Newer data appears only to be occasionally updated.

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  • $\begingroup$ Excellent! I wasn't familiar with Dated. I have previously had vague misgivings about entity properties without dates, but don't use entities enough to have stumbled on Dated. Thanks! $\endgroup$
    – lericr
    Sep 28, 2022 at 20:51

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