how do you explain the "Chinatown" epidemic?

In my hometown, Houston, Chinese, Vietnamese, and some Koreans, pretty much bought all the retail space on Bellaire (South West Houston). There are actually a few economic/ethnic enclaves in Houston, but I'll just speak on the one i've been to the most.

They were 3 Chinese banks (with Chinese speaking tellers)
A few insurance companies, a lot of clothing stores, 1 major asian supermarket (with several other ones around the city, and at least one in Austin), import/export spots, furniture places, doctors and lawyer offices, and hella restaurants, bars and clubs. Keep in mind this is all happening on the span of 6-7 blocks. (and there are other strong holds)

Most of the shopkeepers all spoke some Asian language. It was difficult to ask any sort of questions/get service without having a 'representative' if you will.

You mean to tell me that a Chinatown, that primarily serves their community, but offers goods and services to outsiders (but does not need them), is something that doesn't exist?

I find that very hard to believe. I find it counterintuitive.

Do you have an economic studies to back up your assertions?
Has anyone studied where the money in Asian communities goes?

My Asian friends do buy cars and merino sweaters at the same places I do, but some culturally specific products, they go somewhere else. When it comes time to eat, Korea Garden, Mongolian BBQ, Pho Thai Soon, are all mentioned before Eric's BBQ. If they want to open their own business, and their own banks won't help them out, many pool their family resources (ie no interest or low interest loans), and open up shop.

You've had this line of logic for a while now, and i'm wondering where does it come from, outside of your personal experiences.

Because my personal experiences differ. And I'm more apt to believe my eyes and all the economic build up in the city I grew up in.