We're living in the age of Urbanization Plus, where people aren't just moving from rural areas to cities, they're also moving from smaller cities to bigger cities in large numbers. It wouldn't surprise me if we were all trending towards South Korea your situations where half the population lives in the capital (except in the US - there will be a few cities everyone moves to, but probably not DC).
The problem is jobs. People want to move where the jobs are. Now that farming isn't a big job creator and many factories have moved away then it's all about commerce. That requires a large concentration of people. Cities will often not have enough to offer to make a company move to their city instead of some other city. Especially nowadays when people get really upset over a city offering a good deal to some business (eg Amazon and New York a few years ago).
Yes we are probably trending that way, but I don't see how that's a bad thing. The bad thing is that rural and smaller cities were not able to compete thrive. In the end the centralization of the economy will only increase productivity, but if you want to keep them alive you need to invest in them to justify their existence. We should not be going out of our way to keep them alive, unless they have specific national interests.
If you provide policies that benefit those urban cores at the expenses of rural voters, don't be surprised if the Rust Belts revolts against your plans.
> It wouldn't surprise me if we were all trending towards South Korea your situations where half the population lives in the capital (except in the US - there will be a few cities everyone moves to, but probably not DC).
Though the political capital was moved to the South, economically the effective capital of the US remained (and remains) NYC.
While NYC is great, and our biggest city, etc., one difference from other countries is that New York State (the whole thing), only represents 8.1% of US GDP. Even if you add all of New Jersey and Connecticut, you get about 12.3% of total GDP.
As states, both California & Texas have greater share of GDP than NY.
So US GDP is much less concentrated than in some other countries.
The problem is amalgamation and the fact that western countries (very mistakenly) decided to deindustrialize and send their jobs to poorer countries to prop up their corporate profits. It is much harder for people to graduate and go get a good job at the local factory, have 4 kids, a house, etc. You need to go to college, get a degree, fight for a job which then become more concentrated in fewer places as they compete for workers.
Hopefully remote work will help push back against this force.
The problem is jobs. People want to move where the jobs are. Now that farming isn't a big job creator and many factories have moved away then it's all about commerce. That requires a large concentration of people. Cities will often not have enough to offer to make a company move to their city instead of some other city. Especially nowadays when people get really upset over a city offering a good deal to some business (eg Amazon and New York a few years ago).