A lot of comments about metros areas and the like, such as how Jacksonville shows up because of city limits being larger than atlanta, but if you start getting I to trying to define what a city's metro area is, you run into a lot of issues with giant powerful cities like NY. Can you really count the population of Newark, New Jersey as part of NYC, NY? Even though newark is firmly within the NYC metro area, it's a separate city in a different state with it's own government etc. And what do you do about the bay? Is San Francisco part of san Jose? What about twin cities, like dallas and fort worth? This probably makes the most sense as a way of doing this map since at least it's clear cut.
yes that's exactly what I'm referring to as the problem - the city limits are arbitrary administrative lines. What would not be counted in atlanta as simply part of the suburb would be counted towards the population of jacksonville because the boundaries just happen to be huge, which means jacksonville ends up larger than atlanta, even though more people are in the atlanta metro area and would call themselves as people from atlanta as there are people in the jacksonville metro area
As you get near the outskirts of a city, where you live starts to depend on who you're talking to. I live in Gig Harbor, Washington, which is about 20 minutes from Tacoma, which is itself about half an hour from Seattle. If I was talking to someone else from the area, I'd never claim to live in Seattle. But if I'm talking to someone from out of state, then yeah, sure, I'm from Seattle.
One way to work around the arbitrariness of city limits would be to only count the population living within a fixed distance of the city center. I would suggest 5 or 6 km, which is approximately the distance that your can comfortably walk in 1 hour, and also (perhaps not coincidentally) the approximate radius of Paris. This would get you a list of dense cities, which is probably what people are imagining when they thing of "large" cities.
Another way would be to count everyone as part of the population of whatever city they are physically closest to, without regard to political boundaries. But this would probably just get you a list of sprawling metropolitan areas.
A good way to define metropolitan areas is by commuter patterns. If a certain percentage of residents of a county or town all commute to the same adjoining larger town, then that gets counted.
Not all cities have centers and some cities have multiple different centers that are quite far away from each other depending on what criterion you use.
The choice of geographic unit depends what questions you're interested in answering. If you're trying to answer questions about government, tax base, city services, etc., then you definitely want to use legal/administrative divisions as your unit of analysis. If you're interested in answering demographic questions, like population growth or labor pool, then statistical areas like CBSAs are more useful, because differences in administrative boundaries would introduce inconsistencies in your data.
You can also define a region as an area of (relatively) continuous density - the Census does this and labels them "urbanized areas". Any one of the 3 approaches (administrative boundaries, commuting zones, density) can be reasonable, depending on what sort of questions you'd like to answer.
> Can you really count the population of Newark, New Jersey as part of NYC, NY?
If you're looking at metro areas (which are defined by commuting regions), then you definitely should, because a sizable fraction of the residents of Newark and the surrounding communities commute into NYC for work. The Census does define a sub-unit called metropolitan division, and Newark, NJ is one of these.
> Is San Francisco part of san Jose?
If your unit of analysis is MSA, then no - "San Francisco-Oakland-Hayward, CA" and "San Jose-Sunnyvale-Santa Clara, CA". This division recognizes that the two have separate (but overlapping) commuting zones - very few people commute from Richmond to Sunnyvale, or from Milpitas to San Francisco.
However, they are both within the "San Jose-San Francisco-Oakland, CA" Combined Statistical Area, which is a broader unit which recognizes that there are commuting relationships between the two areas - they are just weaker than the commuting relationships within the MSAs.
> What about twin cities, like dallas and fort worth?
Dallas-Fort Worth-Arlington, TX is an MSA. For the purposes of maps like this, you can generally just take the name of the city that come first in the MSA name and people will understand what you're referring to.
