suburbanization

suburbanization means a decreasing proportion percentage of people living in city core. With deteroirating living environment in city centre (e.g. pollution and traffic congestion, housing problems etc in city centre), some well-off residents cannot withstand the poor living standard in city and move out. Some of them move out along major suburb transportation route (call urban sprawl); some living in suburb satellite towns (forming multiple nuclie); all of them cause a reduction in city centre population.