Transcript Figure 1 - University of Oregon

Chapter 4
Newton=s First Law of Migration:
The Gravity Model
Activity 1: Predicting Migration with the Gravity Model
Activity 2: Scatter Diagram
Activity 3: Residual Map
Activity 4: Evaluation
Learning Outcomes
After completing the chapter, you will be able to:
 Apply principles of spatial interaction to
patterns of movement
 Identify the major source areas for migration to
your state
 Use functions of a spreadsheet
 Produce and interpret a scatter diagram
 Discriminate between positive and negative
residuals
 Identify outliers on a scatter diagram
 Think critically about models in human
geography
Figure 4.1
Age Selectivity of Migration:
Migration Rates 1993-1994
Migration Rate (% of population
moving each year)
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
4
9
14
19
24
29
34
39
44
49
54
59
64
69
74
79
84
89
Age
Source: U.S. Dept. of Commerce, Bureau of the Census. Geographical Mobility: March 1993 to March 1994
Current Population Reports P20-485, p. 3.
Figure 4.2
Migration rates are highest for young adults in their early twenties.
Figure 4.2
Figure 4.3
Figure 4.4
Figure 4.5
Figure 4.6
Gravity Model:
Iij  k
Pi Pj

dij
Iij
=
predicted interaction between origin i and destination j.
k
=
a scaling constant
Pi
=
a measure of size, usually population, for origin I
Pj
=
a measure of size, usually population, for destination j
dij
=
distance between origin i and destination j

=
an exponent which adjusts for the rate of distance decay unique to the type of interaction
being measured
Figure 4.7
Figure 4.8
Figure 4.9
Figure 4.10
Figure 4.11
Figure 4.12
Figure 4.13
Definitions of Key Terms
• Distance Decay:
The declining intensity of an activity with
increasing distance from its point of origin.
• Extreme Value:
A point on a scatter diagram that is roughly in
line with the main trend but is separated from the main group of points
because of its extremely high or low value. Contrast with outlier.
• Gravity Model:
A model to predict spatial interaction, where
size (population) is directly related to interaction and distance is
inversely related to interaction.
• Migration: A permanent change in residence to outside one’s
community of origin.
• Migration Selectivity: The tendency for certain types of people to
migrate. Age, education, and other sociodemographic characteristics
are migration selectivity factors.
• Migration Stream: A well-defined migration channel from a
specific origin to a particular destination.
• Migration Counterstream:
migration stream.
Migration that runs opposite to a
• Outlier:
Point on a scatter diagram that lies far off the trend line.
Outliers on the graph correspond to cases that are poorly predicted by
the model. Outliers are not to be confused with extreme values, which
may lie far from any other point but which are still close to the bestfitting line (see Figure 4.13).
• Pull Factors:
Reasons to move to a particular place.
• Push Factors:
Reasons to move from a particular place.
• Residuals: The difference between an actual observed value of
some variable and its predicted value using the gravity model.
• Scatter Diagram:
A scatter of dots showing the relationship
between two variables. Each dot on the graph represents the x and y
coordinates of a different observation or case.
• Spatial Interaction: Movements of ideas, information, money,
products, and people between places.