The Spatial GINI Coefficient
Dr. Paul C. Sutton
Department of Geography
University of Denver
Population Assocation of America Conference
San Francisco May 3rd, 2012
Outline
• Lorenz Curve and the GINI Coefficient
as a measure of distribution of wealth
• Global gridded representations of
Nighttime Satellite Imagery and
Population Density as an alternative
source for developing a spatially
derived Lorenz Curve.
• The Human Development Index (HDI)
Data Products Used
Nighttime Lights of the World
DMSP OLS (NGDC)
LandScan Global Grid of Population
Scatterplots of Light vs Population for
Pixels in China (left) and U.S. (right)
The Spatial GINI Coefficient I
10 km x 10 km
Population Grid
10 km x 10 km
DMSP OLS Image
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Analysis of the population grid relative to the light grid (above)
produces a table that contrasts % of Population to % of light in
any given country or area (See table below).
Light Level (DN)
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1
2
5
10
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150
255
Pop in DN
205
10
90
55
40
120
200
100
Total Pop = 820
Total Light = 1137
Cum % of Light Cum % of Pop
0.0
25.0
0.1
26.2
1.5
37.2
3.7
43.9
7.2
48.8
24.8
63.4
77.6
87.8
100.0
100.0
The Spatial GINI Coefficient II
(also referred to as the “Lumen GINI”)
The
“Lumen GINI”
Coefficient
Cumulative % of Light
Spatial Lorenz Curve
100
on
i
t
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b
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tr t ion
s
i
l d pula
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u po
q
e st
& o ng
m m
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if ht a
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U lig
of
63.8 % of Pop
80
60
40
20
Pink Area
Yellow Area
with 24.8%
of Light
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Cumulative % of Population
A ‘lumen GINI’ of 1.0
implies one person lives
where all the light is and
everyone else is in the dark.
A ‘lumen GINI’ value of 0.0
implies light is distributed
equally amongst all people.
The “Real” Income GINI Coefficient
Note: Research suggests the United States is on track to pass Mexico
Highly variable ‘freshness’ of Data
Due to the lack of a systematic international data collection system, the data
used to calculate income Gini coefficients span nearly two decades
The Global Spatial GINI
The Lorenz curve for the global Lumen Gini Coefficient,
formed by combining the data from all countries.
Lorenz curves and Lumen Gini
coefficients for six countries
GINI = 0.941
GINI = 0.791
GINI = 0.748
GINI = 0.623
GINI = 0.981
GINI = 0.542
Map of national Spatial GINI
Coefficients
Map of Subnational Spatial GINI
Coefficients
Map of Spatial GINI Coefficients
at a 0.25 degree grid
Spatial GINI vs. Income GINI
National level Lumen Gini versus Income Gini coefficients. Note the poor correlation,
indicating that the two Gini’s are measuring very different phenomena.
Spatial GINI vs Per Capita
Energy Consumption and
Electrification Rates
Spatial GINI vs. Human Development Index
Spatial GINI vs. Human Security Index
Spatial GINI vs. Ecological Footprint
Discussion & Conclusions
The Spatial GINI or Lumen GINI does not measure
distribution of wealth in any manner similar to the
Income GINI.
The Spatial GINI correlates strongly and significantly
with both the Human Development Index (HDI) and
The Human Security Index (HSI).
Simple, empirical measures such as the Spatial GINI
as presented here present an opportunity for improved
spatially explicit characterizations of the human
condition.