I noticed something similar as well, especially in Houston, where the eastern side is much more urban, and the western side is where the expansion has been and is less urban and contains more neighborhoods, smaller grocery stores, etc.

Interesting - typically I would associate "urban" with smaller grocery stores.

i.e. there are 8 grocery stores within a few minutes walk, but they are all smaller - some just sell produce, others are smaller versions of suburban grocery stores.

There seems to be some kind of 'periphery' effect too, in places: zoom in on Portland, Oregon, and it sort of looks like there's a red ring around the town.

I could see it being a 'rural' thing, but the ring is weird.

That could just be from gentrification pushing lower income people out of the city center. Similar things have happened in DC, Chicago, etc. This Wired article shows some of that effect. http://www.wired.com/2013/08/how-segregated-is-your-city-thi...

I don't think so, at least in Seattle. Looking at the city breakdown, it corresponds to transit coverage and (my perception) transit friendliness. It actually seems to correspond inversely against income, since the transit coverage is vaguely inverse with Seattle income.

This is, by the way, a strong conflict with East Coast cities in the US, where there's a decided "obese area" visible. I don't have insight into those from the ground level.

It might be effect of people who have to drive for most trips, versus those who can walk or bike (alone or in combination with transit) to at least a few destinations.

That sort of access also makes those places more desirable, and thus more expensive, and thus more likely to be populated by rich people.

You can see it all over the Western us. Super fascinating.

Walking turns out to be good for you.