I believe a majority in the US lives in a metro area of at least 100,000 people, but only about 30% appear to live in a city of at least 100,000 people.
I think the difference is the suburbs, and I don't think that is a recent thing.
These is no definition of "suburb" just as there is no definition of "downtown". A suburb is just a part a city with less dense housing.
You have:
1. Legal boundaries of cities, which are dependent on the state. Each state has a constitution that determines what the requirements are to be a city. Maybe it's only 10 signatures and filing fee. Maybe it's much more. There is also a well defined process for extending the boundaries. Outside the city you have unincorporated areas, but that's like places where you have to get water from a well and use a septic tank. That's not suburbs, it's country.
2. Because 1) is so random, government statistics office come up with their own definition of "statistical areas". There are metro-statistical area, and micro-statistical areas, and even these depend on which agency made the list.
3. Realtors keep their own definitions.
4. Things like advertisers and business have their own definitions depending on industry (e.g. media markets)
5. locals have their own definition.
At the end of the day, you have to pick a list and work with it, knowing the pros and cons and how that affects your methodology.
I'm from LA. We refer to the entire metro area as "LA" or the "city"; basically, from Six Flags in the north to the Orange Curtain in the south, and from the beach to Pomona. And that whole area has been ballooned with speculation to the point where no one can buy a house on a normal salary. I still see no reason anyone needs to live there at the current prices. I encourage everyone I know who still lives there to just get out.
Right... we call these little suburbs "cities". City of Palo Alto. City of Berkeley. But we also pretty much consider the Bay Area as one big city, or maybe 3 if we're old school. If you say "Bay Area" anywhere, everyone knows you mean that giant beard that runs all over the bay.
For example the New Jersey has 52 cities - in a state with a population of just 8.8 million, so each 'city' only has on average 170k people - and that's if they all lived in a city! Many have populations in the low four-figures.
I'm not an expert on New Jersey, but there are signs everywhere for "Twps" which I guess are "townships". I'm guessing probably a lot of people live in them.
In New York State, a "town" seems to be not exactly a town, like a stereotypical "small town".
I've lived here most of my life and never really realized, but according to Wikipedia, a "town" in NY is more or less the equivalent to a "township" and within it are "villages".
"every piece of land in the State is part of a city or town, which, with the exception of the city of Geneva, is part of one and only one county. Not every piece is in a village or city. A village is part of a town; cities are not part of towns, but have the powers of towns. A village can be a part of more than one town. A village cannot be part of a city."
So more like a division of a county that's not part of a city than an actual town.
And where this is going, is that I think this is where a lot of people live, rather than cities per se.
An administrative division, where a lot of people live, that's neither a city nor a village, but has water and sewer and so on, sounds to me like almost a definition of suburbs.
You have:
1. Legal boundaries of cities, which are dependent on the state. Each state has a constitution that determines what the requirements are to be a city. Maybe it's only 10 signatures and filing fee. Maybe it's much more. There is also a well defined process for extending the boundaries. Outside the city you have unincorporated areas, but that's like places where you have to get water from a well and use a septic tank. That's not suburbs, it's country.
2. Because 1) is so random, government statistics office come up with their own definition of "statistical areas". There are metro-statistical area, and micro-statistical areas, and even these depend on which agency made the list.
3. Realtors keep their own definitions.
4. Things like advertisers and business have their own definitions depending on industry (e.g. media markets)
5. locals have their own definition.
At the end of the day, you have to pick a list and work with it, knowing the pros and cons and how that affects your methodology.