What are the reasons behind the existence of pockets of poverty in the United States?

Question 1:

  1. What are the reasons behind the existence of pockets of poverty in the United States?
  2. Why did the middle class move out of the cities? Do race and ethnicity play a role or is it all social class?
  3. The move to the suburbs has been accelerated. What are the reasons?
  4. What advantages exist to living in the city?

Question 2:

While most of the attention regarding population problems focuses on population growth, there is growing concern about the exact reverse: birth rates that are at or below replacement level in some industrial countries.

  1. What impact can low birth rate have on a country?
  2. Why are some countries facing low fertility rate (lower than 2.1)?