Which of the following best explains what the centric zone model and bid rent curve illustrate about patterns of urban areas?

Explain the spatial pattern of economic activity, the zoning of urban and suburban functions and the internal structure of the central business District (CBD)... 

The video below shows what happens on a walk across London. It highlights the relatively small size of the CBD compared to the residential areas around it.

Part 1: EXPLAIN THE SPATIAL PATTERN OF ECONOMIC ACTIVITY

Key terms
Economic activity:  the production and consumption of products (goods and services). The amount and type of economic activity varies across the urban area.
CBD: Central Business District, commonly known as the city centre.

Urban Models
The general spatial pattern of economic activity can be described using the same models that are used for residential patterns. The models below are better known as:
Burgess - concentric zone model
Hoyt - sector model
Ullman and Harris - multiple nuclei model

Each of these has some significant drawbacks (they are only applicable to very general situations, they are simplistic in refusing to acknowledge that within each zone there can be significant differences, and they do not adequately explain the distribution of economic activity around urban areas). However, they do summarise a large amount of information in one place.

Bid Rent Theory
This is sometimes known as the land value model. 
The cause of this spatial variation in economic activity can be explained using the Bid-Rent Theory. This model is based on the competition for the best land. The activity that makes the highest profit from the smallest amount of land can pay the highest amount and choose the most desirable location.
Economic activity in this model is split into commerce (shops, offices, leisure activities) and industry (manufacturing, transport, warehouse storage). 

The model assumes that the CBD is the best location for economic activity. This is for several reasons:
- because it generally is the nodal point for transport networks
- it is the easiest part of the city to access both in terms of distance and transport
- agglomeration and functional grouping is facilititated by having similar types of economic activity close together

Therefore, all activities desire to be near to the CBD. Due to the shortage of space, and the competition from various economic activities, the prices in this area are the highest. This means that commerce, which requires the least amount of space and makes the most profit, can afford to out-bid the competition. The second zone, around the CBD, is occupied by the next highest bidder (industry), and so on.

Though the Bid Rent Theory makes most sense in relation the Burgess Model, it can be used in a simlar way to explain secondary land value peaks, where secondary transport nodes push up the price. Fundamentally, the model is suggesting that it is the value of land that creates zones where commerce and industry are found.

The PLVI
The PLVI is the Peak Land Value Intersection. It refers to the point in the CBD which has the highest value. More information about this can be found in Part 3 below.

Note that this is presenting a very traditional view of the city and more detail will be found about today's economic activity (especially with reference to out-of-town sites) in the section 'The movement of economic activity'. It is also highly Westernised in its outlook - cities in Asia, Africa, Oceania and South America frequently follow different patterns as shown in the models of cities for those regions. However, the explanation remains similar - proximity to transport results in higher land values which results in occupancy by the highest profit economic activity.

Part 2: EXPLAIN THE ZONING OF URBAN AND SUBURBAN FUNCTIONS

Key terms

Function: The main activity of a settlement e.g. government centre, financial centre, industrial centre, commercial centre
Urban*: Built-up areas. In this context, it goes beyond 'towns and cities' to refer to the core areas and not necessarily those hybrid areas on the city edge which have very low density housing
Suburban*: An area of residential buildings, especially on the outskirts of a city.
Zoning: The division of an area according to criteria e.g. separating areas into types of residential housing, or types of economic activity.
Agglomeration: Closely associated businesses locate close to one another, and the links between them are increased. This is a similar concept to that in urban agglomeration where cities grow into each other.
Functional grouping: Businesses of the same kind locate near to each other. For example, fashion shops are located in a particular street of a CBD, and jewellery shops are located together in a different street.
*Note that these terms are highly country specific. In many ways, Ma On Shan in Hong Kong is a new-town suburb, though it is made up almost entirley of towerblocks (see below!).

Types of function
Almost every settlement has several functions. However, most settlements prior to the 20th century could also be clearly identified as mainly:

• Market Town - where farmers buy and sell goods
• Port - where goods are loaded and unloaded by ship
• Industrial Town - where most people living there work in factories
• Resort - a place where tourists visit to enjoy themselves

With globalization and the New Division of Labour (in which industry has moved to Newly Industrialised Countries such as Malaysia, Brazil, China and Taiwan), these traditional functions could be updated:

• Commercial centre - where the purchase of goods and provision of services is the main activity (this includes financial centres like Singapore and Hong Kong)
• Distribution and transport - where goods are transferred from one means of transport to another, e.g. a port or a railhead city
• Industrial Town - where most people living there work in factories (note that 'factories' includes food processing, specialised manufacturing, and research and development industries)
• Leisure and recreation centre - a place where tourists and locals visit to enjoy themselves

Other functions
These include

• Government centre
  
• Entertainment
• Offices
• Religious centre
• Port and trade area
• Special economic zone (e.g. free trade zones in some cities to expand exports)
• Historical centre

Zones and functions in urban areas

Retailing
In each of the zones (see models in Part 1, above) some retail will occur. In the CBD, the market is for high-order products. These are goods and services which:
- are expensive
- are bought infrequently
- a person would be willing to travel a long way to purchase
They can also be known as 'comparison products' because the consumer is likey to look at several versions before choosing exactly what to buy. Examples are clothes, electronic items, and specialist products.
In the other zones, retail is likely to involve low-order, or convenience products. These are 
- cheaper
- bought frequently
- bought locally
Examples include standard food items such as vegetables or chocolate - it's unlikely that someone would travel for over 30 minutes in the hope of finding a cheaper Mars bar!
The reason these activities are zoned in this way (i.e. split between CBD and the rest of the city) is that convenience products are purchased near to where people live and work. Therefore it's important to remember that low-order goods can be found in the CBD too. However, they are likely to be more expensive as the profit margins need to be higher to pay the rent.
Important note about retailing: see the section on the movement of economic activity to see how this separation looks today, especially with reference to out-of-town shopping centres.

Finance
Banking and office spaces are usually located in the CBD. The most important part of the 'production' of offices is people, so being in a central location allows easy access for most staff.
Another major reason for the zoning of this function is agglomeration and functional grouping. This allows them to share expertise but more importantly attract customers and skilled staff more effectively than if they were spaced further apart. In economic sectors such as finance, the links between banks are frequently as important as the links between the bank and its customers.
By locating in the CBD, there is a level of prestige associated with being in the most central location. London, New York and Hong Kong all have finance districts in which instritutions compete with one another for the tallest building, most impressive entrances and so on.
However, once again, this is changing! As companies of all kinds begin to look for more ways to make profit, banks too are moving location. This will be dealt with in the section on the movement of economic activity.

Industry
For most HICs, industry is now a relatively small part of their economy. In the UK, arond 77% of the economy comes from the service sector (2013 figures)! Therefore, industry tends to be limited in its importance.
The industry that has remained is often light industry - e.g. manufacturing of small products like specialised electronics. These firms make large profits but tend to locate in the outskirts of the city where transport (which is likely to be by road) is more accessible. These industries are largely footloose, meaning they have no particular need to locate in any place due to raw materials, transport or energy, and so they are able to move with ease.

Residential
Low class housing (small housing, generally old, poor quality building materials,  no outside space, limited toilet/bathing facilities, lack of heating and/or appropriate climate control) is generally found in the area around the CBD known as the inner city, as it was originally intended for the workers of the factories during the industrial revolution. Over the second half of the 20th century, this type of housing has also been constructued in large estates on the city edge, often by governments. This was an effort to reduce the amount of poor quality housing, and to make space for the increasing population of urban areas. 
More recently, gentrification has led to the modernisation of poor housing in inner city areas.
The further from the CBD, the better the quality of housing becomes. This is partly because the wealthier inhabitants can afford the higher costs of this type of housing and the increase costs of transport to work in the CBD. It is also because the cheaper land values (see bid rent theory) make it possible to purchase more land, and therefore construct larger houses with more private space around them. 
Again, this fits a very Westernised model of urban development. Hong Kong's Ma On Shan (see picture above) is largely made of high-class residential apartment buildings with swimming pools, gyms and clubhouses being a standard feature. The high land prices in the main part of the city of Hong Kong (spread across the northern part of the island and the Kowloon peninsula) have resulted in a highly mixed development.

Part 3: EXPLAIN THE INTERNAL STRUCTURE OF THE CENTRAL BUSINESS DISTRICT (CBD).


Key terms
Core-frame model - a graphic representation of the CBD split into three main zones of the core (centre), frame (edge) and area between (outer core). 
Land use - the activity and buildings occupying space e.g. offices, shops, restaurants. This can also refer to the type of offices and shops e.g. fashion outlets or banks.
Internal structure - the spatial distribution of funtions within the CBD.
Footfall - the number of people walking past a particular location

What is the CBD?
The main features of the CBD are (source: Geography, An Integrated Approach by David Waugh, p430).
- Major retailing outlets
- Offices
- Tallest buildings due to high rent per square foot of land
- Greatest concentration of pedestrians
- Highest concentration of traffic
- Highest land values
- Most dynamic area

It's important to remember why this all occurs: it's both the cause and consequence of the Peak Land Value Intersecction.
Highest land values at the PVLI…
…due to ease of access…
…and therefore high bid-rent…
…and therefore high-order services and retail…
…and therefore need to maximise profits…
…and therefore internal zoning (clustering)…
…and therefore the development of a core and frame...
...which we put into the Core Frame Model.

In this diagram, the Inner Core is located where the PLVI is found - the Peak Land Value Intersection. This PLVI is there because of the best transport links, although it is usually located to the edge of the actual location of rail stations etc. which take up large amounts of space and restrict development.

The majar parts are:
Inner Core - the location rarely changes, because this area contains the best transport links. In this area, the highest order shops and highest profit office activities are found.
Outer Core - these are similar activities to the Inner Core, but require more space e.g. cinemas, or are have lower profit levels e.g. non commercial office activities such as local government.
Frame - this is the edge of the CBD. It includes the major transport terminals, and activities that directly support the CBD.
Zone of Assimilation - an area that is relatively fluid and can move. This corresponds closely to the gentrification argument - an area of low quality becomes fashionable, resulting in an increase of income which can then extend the CBD in that direction.
Zone of Discard - an area becomes run down, often due to a major employer closing down and/or a lack of investment in the urban infrastructure.

Part 4: DESCRIBE THE INFORMAL SECTOR; ITS CHARACTERISTICS AND LOCATION IN URBAN AREAS.

Key terms
•Informal sector: Work done that is “spontaneous and/or irregular” and is not recognised as a normal income source
•Black economy: Illegal economic activities which are not controlled or permitted by the government
•Shadow economy: More politically correct term for black economy
•Squatter settlement: The correct UN term for a makeshift settlement (self-built settlement)
•Slum: A common term for a squatter settlement (an unplanned area of housing) but can also refer to poor quality / degraded housing
•Shanty town: A common term for squatter settlement, especially in south Asia (India). It is often considered derogatory. In South America the term is commonly favela, and also known as bustee in India.
•Paratransit: Any form of community transport, including informal transport such as rickshaws and taxi buses, following no fixed route or schedule.

The location of squatter settlements

World distribution The map to the right shows the territory size according to the proportion of worldwide population that live in slums that live there (2001 figures).  The majority of the squatter settlement population is in Asia, followed by Africa and South America.

Source: http://www.worldmapper.org/display.php?selected=187

Within cities: urban models The models to the right show the distribution that is typical in LICs. The zone around the CBD is of high class housing because the transport infrastructure is poor in these cities, so it would take a long time to travel to the CBD from the outskirts. At the same time, recent in-migrants to the city are forced to build their own houses, and do this on unwanted or empty land towards the edge of the city where room is available. The result is an inverted pattern compared to HICs, with only the CBD remaining in the same location in the city model.

Source: http://geographyfieldwork.com/UrbanModelsLEDCs.htm

Key characteristics of informal economies

• Poverty - generally the poorest in the urban area, but also some 'middle class' stepping into service areas such as paper rounds, babysitting, gardening
  
• Labour - unskilled
  
• Employment - no formal contract
  
• Age - all ages, but most likely among youth who have not built up a skill set
  
• Skills - significantly lacking
  
• No set hours
  
• Location - usually in the frame area of the CBD and clustered in areas of high footfall
  
• Criminal activity? 

Benefits of the informal economy

• Reduces the burden on the state for supporting low-income groups
• Provides large numbers of casual workers, which are ideal for developing countries
• Allows the economy to grow despite cumbersome laws and high taxes in LICs and MICs
• Produces cheap goods
• Allows the economy to react quickly to new opportunities and threats (e.g. workers can be hired without bureaucratic procedures)

Drawbacks of the informal economy

• Potential for criminal activity as the law is not in control
• Workers are trapped in poverty
• Lack of healthcare, paid vacation etc. for workers
• Frequently unsafe activities undertaken

Case study of informal employment: The Zabbaleen, Cairo

The Zabbaleen area a group of informal workers in Cairo. They specialise in recycling. The following videos show their work and describe the value of what they do, as well as showcasing the problems (and potential solutions) they face.

Which site factor best explains the linear pattern of urbanized areas?

Which of the following statements best explains how the world cities listed in the table function within the world's urban hierarchy quizlet?

Which of the following best illustrates how the world cities in the table are connected globally in ways that?

Which of the following best explains how the model is limited in its representation of present day urban land use patterns?