[B][U]CBD[/U][/B]
The CBD or Central Business District is the Core of the City

The CBD or Central Business District is focal point of a city. It is the commercial, office, retail, and cultural center of the city and usually is the center point for transportation networks

[B][U]The Modern CBD[/U][/B]
By the beginning of the 21st century, the CBD had become a diverse region of the metropolitan area and included residential, retail, commercial, universities, entertainment, government, financial institutions, medical centers, and culture. The experts of the city are often located at workplaces or institutions in the CBD – lawyers, doctors, academics, government officials and bureaucrats, entertainers, directors and financiers.

In recent decades, the combination of gentrification (residential expansion) and development of shopping malls as entertainment centers have given the CBD new life. Once can now find, in addition to housing, mega-malls, theaters, museums, and stadiums. San Diego's Horton Plaza is an example of redeveloping the downtown as an entertainment and shopping district.
Pedestrian malls are also common today in CBDs in an effort to make the CBD a 24 hour a day destination for not only those who work in the CBD but also to bring in people to live and to play in the CBD. Without entertainment and cultural opportunities, the CBD is often far more populated during the day than at night as relatively few workers live in the CBD and most do commute to their jobs in the CBD.


[B][U]The Peak Land Value Intersection[/U][/B]
The CBD is home to the Peak Land Value Intersection in the city. The Peak Land Value Intersection is the intersection with the most valuable real estate in the city. This intersection is the core of the CBD and thus the core of the metropolitan area. One would not typically find a vacant lot at the Peak Land Value Intersection but instead one would typically find one of the city's tallest and most valuable skyscrapers.

The CBD is often the center of a metropolitan area's transportation system. Public transit as well as highways converge on the CBD, making it a very accessible to those who live throughout the metropolitan area. On the other hand, the convergence of road networks in the CBD often creates overwhelming traffic jams as commuters from the suburbs attempt to converge on the CBD in the morning and return home at the end of the work day.


[U][B]Edge Cities[/B][/U]
In recent decades, edge cities have begun to develop as suburban CBDs in major metropolitan areas. In some instances, these edge cities have become a larger magnet to the metropolitan area than the original CBD.

[B][U]Defining the CBD[/U][/B]
There are no boundaries to the CBD. The CBD is essentially about perception. It is usually the "postcard image" one has of a particular city. There have been various attempts at delineating the boundaries of the CBD but, for the most part, one can visually or instinctively know when the CBD starts and ends as it is the core and contains a plethora of tall buildings, high density, a lack of parking, transportation nodes, a large number of pedestrians on the street and generally just a lot of activity during the daytime. The bottom line is that the CBD is what people think of a city when they think of its downtown area

economic sectors og geography
 

A nation’s economy can be divided into various sectors to define the proportion of the population engaged in the activity sector. This categorization is seen as a continuum of distance from the natural environment. The continuum starts with the primary sector, which concerns itself with the utilization of raw materials from the earth such as agriculture and mining. From there, the distance from the raw materials of the earth increases.

[B][U]Primary Sector[/U][/B]
The primary sector of the economy extracts or harvests products from the earth. The primary sector includes the production of raw material and basic foods. Activities associated with the primary sector include agriculture (both subsistence and commercial), mining, forestry, farming, grazing, hunting and gathering, fishing, and quarrying. The packaging and processing of the raw material associated with this sector is also considered to be part of this sector.

In developed and developing countries, a decreasing proportion of workers are involved in the primary sector. About 3% of the U.S. labor force is engaged in primary sector activity today, while more than two-thirds of the labor force were primary sector workers in the mid-nineteenth century.


[B][U]Secondary Sector[/U][/B]
The secondary sector of the economy manufactures finished goods. All of manufacturing, processing, and construction lies within the secondary sector. Activities associated with the secondary sector include metal working and smelting, automobile production, textile production, chemical and engineering industries, aerospace manufacturing, energy utilities, engineering, breweries and bottlers, construction, and shipbuilding.


[B][U]Tertiary Sector[/U][/B]
The tertiary sector of the economy is the service industry. This sector provides services to the general population and to businesses. Activities associated with this sector include retail and wholesale sales, transportation and distribution, entertainment (movies, television, radio, music, theater, etc.), restaurants, clerical services, media, tourism, insurance, banking, healthcare, and law.

In most developed and developing countries, a growing proportion of workers are devoted to the tertiary sector. In the U.S., more than 80% of the labor force are tertiary workers.


[B][U]Quaternary Sector[/U][/B]
The quaternary sector of the economy consists of intellectual activities. Activities associated with this sector include government, culture, libraries, scientific research, education, and information technology.


[U][B]Quinary Sector[/B][/U]
Some consider there to be a branch of the quaternary sector called the quinary sector, which includes the highest levels of decision making in a society or economy. This sector would include the top executives or officials in such fields as government, science, universities, nonprofit, healthcare, culture, and the media.