[m_mueller]

I really don’t see how this keeps coming up as an excuse. East coast corridor is at least as dense and is not far off in purchase power per capita. Plus you could as well compate to China, another huge country with low density of purchase power, and look how they‘re charging ahead in infrastructure. It‘s the political system - not to say that the US should adopt China‘s of course, just that it‘s a better explanation of what goes wrong.

[theredbox]

All chinese subways are in large densely populated cities.

[magduf]

So are the ones in America. However, the ones in America are barely functioning and are a complete disaster.

[aylmao]

> low density of purchase power

I think the commenter was referring to the fact purchasing power is not dense (ie, dense areas don't have as high a purchasing power)? A little confused by this too.

[m_mueller]

just to expand on this a bit:

I like looking at purchase power in general, rather than GDP - the absolute numbers don't matter so much as long as your domestic market is large enough to produce most things people need.

Secondly, the density of savings and taxes per square kilometer is giving you an idea about how much potential for development a current settlement has. That's the capital that can be drawn from directly. Density of spendings (train tickets, consumer goods etc.) is the driver for outside capital to come in trying to get a dividend. Taken all together (savings + spendings) you get the density of PPP adjusted GDP per square kilometer as a figure that matters. As you can see in [1], US and China is actually quite similar in this metric, and it's probably also still similar if you just take its coastal regions. I also think that this metric is very similar for the population belt between London and Rome, and the East Coast corridor in the US.

[1] http://mecometer.com/topic/gdp-ppp-per-square-kilometer/