[epistasis]

Which of these cities is even near to the physical limit?

I think you're getting downvoted because none of them are at any sort of physical limit.

Density is amazingly good for humans: it promotes huge amounts of intellection and economic growth.

Density is what so much of the country is yearning for, and being denied by prior generations and entrenched wealthy residents.

There's only one place density should go: cities. And they have a ton of room for growth in the US to even match other dense cities in world, such as Paris.

[metapsj]

physical limit is probably to narrow to effectively argue my original position. there are many limiting factors including physical boundaries of geography. consider the political climate, economic environment, accumulated technical debt of past construction practices, artificial boundaries development by cities to bolster real estate values, not to mention investments made by individual home owners and businesses. there are a lot of forces at play to gain consensus especially when you have significant momentum moving along a trajectory started easily 30 years ago that led us to where we are today. and not to mention the accumulated debt of a city like san francisco which the last i read was at $10B. these forces are like concrete or better yet non-newtonian in nature, the more you stir the pot the more rigid it becomes.

i agree there are a lot benefits to density, i'm not down playing those benefits. but i do think we have a lot of great technology in play and coming down the pipe that allows us to have many of the same benefits across large geographic areas.

also i feel large cities are captive to it's wealthy benefactors whether it's a company, an individual, or a politician who wields influence.

more importantly, it's far easier to create incentives to entice companies with high economic value and high paying jobs to an area with few competitive forces.