The Gravity Model
Site
The site is the actual location of a settlement on the earth and is composed of the physical characteristics of the
landscape specific to the area. Site factors include things like landforms (i.e. is the area protected by mountains or is
there a natural harbor present?), climate, vegetation types, availability of water, soil quality, minerals, and even
wildlife.
Situation
Situation is defined as the location of a place relative to its surroundings and other places. Factors included in an
area's situation include the accessibility of the location, the extent of a place's connections with another, and how
close an area may be to raw materials if they are not located specifically on the site.
Central Place Theory
Marketing/City
Hierarchy Model
Transportation Model
Administrative/
Government Model
Christaller's Assumptions
To focus on the economic aspects of his theory, Christaller had to create a set of assumptions. He decided for example that the
countryside in the areas he was studying would be flat, so no barriers would exist to impede people's movement across it. In
addition, two assumptions were made about human behavior: 1) Christaller stated that humans will always purchase goods from the
closest place that offers the good, and 2) whenever demand for a certain good is high, it will be offered in close proximity to the
population. When demand drops, so too does the availability of the good. (Economic Man (who knows all))
In addition, the threshold is an important concept in Christaller's study. This is the minimum number of people needed for a central
place business or activity to remain active and prosperous.
Leads to concept of high-low order Goods and Services
Losch’s Central Place Theory
In 1954, German economist August Losch modified Christaller's central place theory because he believed it was too rigid.
He thought that Christaller's model led to patterns where the distribution of goods and the accumulation of profits were
based entirely on location. He instead focused on maximizing consumer welfare and creating an ideal consumer landscape
where the need to travel for any good was minimized and profits were held level, not maximized to accrue extra.
Central Place Theory Today
Though Losch's central place theory looks at the ideal environment for the consumer, both his and Christaller's ideas are
essential to studying the location of retail in urban areas today.
Factors shaping the extent of market areas:
1. Land use: industrial areas can provide little in the way of a consuming population
2. Poor accessibility: this can limit the extent of a center's market area
3. Competition: this limits the extent of market areas in all directions
4. Technology: high mobility afforded by the automobile allows overlapping of market areas
Examples of Countries With Primate Cities
Paris (9.6 million) is definitely the focus of France while Marseilles has a population of 1.3 million.
Similarly, the United Kingdom has London as its primate city (7 million) while the second largest city, Birmingham,
is home to a mere one million people.
Mexico City, Mexico (8.6 million) outshines Guadalajara (1.6 million).
A huge dichotomy exists between Bangkok (7.5 million) and Thailand's second city, Nanthaburi (481,000).
Examples of Countries that Lack Primate Cities
India's most populous city is Mumbai (formerly Bombay) with 16 million; second is Kolkata (formerly Calcutta) with
more than 13 million; and third is less than 13 million.
China, Canada, Australia, and Brazil are additional examples of non-primate-city countries.
Utilizing the metropolitan area population of urban areas in the United States, we find that the U.S. lacks a true
primate city. With the New York City metropolitan area population at approximately 21 million, second ranked Los
Angeles at 16 million, and even third ranked Chicago at 9 million, America lacks a primate city.
The Law of Retail Gravitation
In 1931, William J. Reilly was inspired by the law of gravity to create an application of the gravity model to measure
retail trade between two cities. His work and theory, The Law of Retail Gravitation, allows us to draw trade area
boundaries around cities using the distance between the cities and the population of each city.
Reilly realized that the larger a city the larger a trade area it would have and thus it would draw from a
larger hinterland around the city. Two cities of equal size have a trade area boundary midway between the two cities.
When cities are of unequal size, the boundary lies closer to the smaller city, giving the larger city a larger trade area.
Reilly called the boundary between two trade areas the breaking point (BP). On that line, exactly half the
population shops at either of the two cities.
Edge City
They're called suburban business districts, major diversified centers, suburban cores, minicities, suburban activity centers, cities of
realms, galactic cities, urban subcenters, pepperoni-pizza cities, superburbia, technoburbs, nucleations, disurbs, service cities,
perimeter cities, peripheral centers, urban villages, and suburban downtowns but the name that's now most commonly used for places
that the foregoing terms describe is "edge cities."
Garreau established five rules for a place to be considered an edge city:
1. The area must have more than five million square feet of office space (about the space of a good-sized downtown)
2. The place must include over 600,000 square feet of retail space (the size of a large regional shopping mall)
3. The population must rise every morning and drop every afternoon (i.e., there are more jobs than homes)
4. The place is known as a single end destination (the place "has it all;" entertainment, shopping, recreation, etc.)
5. The area must not have been anything like a "city" 30 years ago (cow pastures would have been nice)
Garreau identified 123 places in a chapter of his book called "The List" as being true edge cities and 83 up-andcoming or planned edge cities around the country. "The List" included two dozen edge cities or those in progress in
greater Los Angeles alone, 23 in metro Washington, D.C., and 21 in greater New York City.