An
innovation or
idea that develops in a
source area
and remains strong there while also spreading outward (the innovation, idea, or disease is moving).
Thus, the innovation spreads in a
snowball effect so that the total number of
adopters and the area of
occurrence increases.
There are three types of expansion
diffusion:
Contagious Diffusion - a form of expansion diffusion in which nearly all adjacent individuals are affected.
An example of this is the spread of
Islam from its
hearth on the Arabian Peninsula to
Egypt and North
Africa, through Southwest
Asia, and into West Africa.
Hierarchical Diffusion - the main channel of diffusion is some segment of those who are
susceptible to (or
adopting) what is being diffused.
An example of this is the spread of AIDS in the United States. Not everyone is affected, only particular vulnerable groups are affected.
AIDS doesn't affect in
certain areas but instead appear as
clusters in distantly separated cities on the map.
Another example is the acceptance of a new style of clothing or new hairstyle. A good number of women adopted the beehive hair-do in the 60's, but not all..
Stimulus Diffusion - a small portion of the
population accepts the idea or
innovation. This is a local
occurance. Some ideas are simply too vague, too unattainable, or too practical for immediate adoption.
An example of this is
industrialization. During the time of the
industrial revolution, only the countries with the
capital and the
resources were able to industrialize while some lesser developed countries still have not.