> 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.
Though the political capital was moved to the South, economically the effective capital of the US remained (and remains) NYC.