American cities are similar to other cities around the world. In every country, cities reflect the values of the culture. Cities contain the very best aspects of a society: opportunities for education, employment, and entertainment. They also contain the very worst parts of a society: violent crime, racial conflict (种族冲突), and poverty. American cities are changing, just as American society is changing.
After World War Ⅱ, city residents became wealthier, more prosperous. They had more children. They needed more space. They moved out of their apartments in the city to buy their own homes. They bought houses in the suburbs, areas near a city where people live. These are areas without many offices or factories. During the 1950s the American "dream" was to have a house in the suburbs.
Now things are changing. The children of the people who left the cities in 1950s are now s. They, unlike their parents, want to live in the cities. Many young professionals, doctors, lawyers, and executives (执行官，行政官), are moving back into the city. Many are single；others are married, but often without children. They prefer the city to the suburbs because their jobs are there; they are afraid of the fuel shortage; or they just enjoy the excitement and opportunities which the city offers. A new class is moving into the city ——a wealthier, more mobile class.
Only a few years ago, people thought that the older American cities were dying. Some city residents now see a bright, new future others see only problems and conflicts. One thing is sure: Many dying cities are alive again.
The movement of people to and from the city can explain______.