Important Phrases Suburbanization is a term used to describe the rise of areas on the outskirts of large cities, which is one of the numerous reasons of urban sprawl. The phrase "rural flight" refers to people's migration tendencies from rural to urban regions. Migration can be for any number of reasons, but usually it is because there are jobs in the city and not in the country. Suburbs were originally rural settlements near towns or cities. As cities grew, they needed more space, so they began to expand outwards, creating suburbs. At first, these new suburbs were just collections of small farms, but as industries started moving away from cities they needed places to house their employees, so factories and office parks were built in this newly developed area called the "office park district". These districts often have a special zoning code that allows for a higher density of buildings than would normally be allowed in a suburb. The office park district is where most corporate offices are now located, instead of inside the city limits. This is because it is more convenient for them to have close access to public transportation than to have to provide for one car per employee. In addition, the office park district provides more room for businesses to grow compared to city centers, which often have limited space. Another reason for suburban growth is the desire for privacy.