AP Human Geography
Thinking Geographically
DIFFUSION
I.
Diffusion’s curve – adoption of a phenomenon
A.
Follows an “S” shaped curve
1.
Example: a.
Beginning Phase: When cell phones first came out, not many people had them because few people knew about them and few distributors offered them for sale. The people who first adopt a practice as it begins to diffuse are called the innovators.
b.
Middle Phase: Later the number of adopters grew by a huge amount as those who had cell phones told others, who could afford them, about the product.
The majority of the people who will adopt the phenomenon do it in the middle phase. These people are called majority adopters.
c.
End Phase: Ultimately, the number of people adopting the cell phone tapered off – the number of susceptible people (people who didn’t have a cell phone but could afford one) shrank and the novelty wore off. The people who do adopt at the end are called laggards.
2.
There is never 100% adoption – there are always people who hold out. There are still people today who don’t own a cell phone.
3.
Many products or diseases taper off at levels much smaller than 100% . If the saturation rate is 10%, then the innovators might just be the first one percent.
II.
Kinds of Expansion Diffusion
A.
Contagious
1.
Rapid, widespread diffusion of a phenomenon throughout population
2.
Places near the origin are usually affected first. The farther you are from the points of origin, the later you will be affected.
3.
Like a pebble tossed in a pond
4.
Influenced strongly by distance – you’re more likely to come into contact with nearby people

5.
Spread of Islam; rapid adoption of AIDS prevention medicine in U.S.; ideas on the
Web
B.
Hierarchical Diffusion
1.
Spread of a phenomenon/idea from persons or nodes of authority to other persons/places
2.
Phenomenon spreads to major cities (maybe even starts there), then to intermediatesize places, then to small towns/rural areas. People in big cities have more access to new phenomenon and are more willing to change
3.
Fashion fads that start in London, New York and then spread; “punk rock” originated in London and New York and spread
* Often times, both types of above diffusion are at work. An indicator of which is dominant is the extent to which the innovation skips over large areas in jumping from city to city (hierarchical) versus the extent to which it spreads like a wave
(contagious). Also, for it to be hierarchical, the larger cities should have significantly more cases.*
C. Stimulus Diffusion
1. Spread of an underlying fundamental idea, although not the specific
trait/phenomenon to a receptive audience who adopt the fundamental
idea
2.
European American settlers spread the concepts of writing, but NOT a specific system of writing to at least one Native American group; Apple computers pioneered certain principles that were adopted, but their computers didn’t do very well.
* Please note – no reference has been made to relocation diffusion*
III.
Barriers to Diffusion
A. Time and Distance decay: the further an innovation is from its source, the less likely it is to be adopted; same with time, the acceptance of an innovation becomes less likely the longer it takes to reach particular adopters
B. Cultural Barriers: language, religion, history, and others
C. Physical Barriers: isolation because of oceans, mountains, climate etc.
D. Examples of Diffusion Barriers:
1. Walmart: started small (in Arkansas) and saturated areas around an urban area before moving into the urban area (hierarchical diffusion in reverse)
--Why hasn't Walmart succeeded in New England? A destroyer of "Main Street" family-run shopping districts, which New England won't allow