ความเหลื่อมล้้าทางเศรษฐกิจ
35
(1) Inequality of “outcomes”: refers to the distribution of incomes
(or other welfare dimension) resulting jointly from the efforts
made by a person and the particular circumstances under which
this effort is made; it is mostly concerned with income
inequality
(2) Inequality of “opportunities”: refers to the heterogeneity in
personal circumstances that lie beyond the control of the
individual, but that nevertheless affect the results of his efforts,
and possibly the levels of those efforts themselves (Roemer,
1998: John Rawls, Amartya Sen and others) eg. Unequal access
to public services etc.
ความเหลื่อมล้้าทางเศรษฐกิจ
36
• If there is equality of opportunities then resulting income
inequality reflects the results of a fair system because it reflects
differences individual talents, efforts and accomplishments.
• This can be counteracted by income mobility (refers to the
amount of movement across income ranks experienced by
persons or families). This implies looking at inequality in longterm.
• Data typically allows us to analyse distribution of outcomes
(monetary and non-monetary); difficult to capture and measure
distribution of opportunities (see paper by Bourguignon and
Ferreira in reading list for discussion and example…)
ท้าไมต้องให้ความส้าคัญกับความเหลื่อมล้้าทางเศรษฐกิจ
37
Ethical and moral reasons: similar individuals should not be treated
differently
Functional reasons: inequality may affect prospects for economic
growth and poverty reduction
• Rising income inequality slows down the poverty reducing
effect of growth
• High initial income inequality reduces subsequent poverty
reduction; it is possible for inequality to increase sufficiently
high to result in rising poverty (Ravallion)
• Inequality impacts on level of growth that is possible;
therefore potential to reduce poverty will be affected
1.4 การวัดความเหลื่อมล้้า
Key indicators
• Share of income received by top 20% or bottom 20%
• Ratio of top 20% to bottom 20% income (or
consumption expenditure)
• Relative mean deviation
• Coefficient of variation
• Gini coefficient
• Generalised inequality index measures
38
1.4 การวัดความเหลื่อมล้้า (cont.)
• Gini Coefficient is a well-known tool for measuring
inequality of income. The value of Gini coefficient ranges
from 0 (=perfect equality) to 1 (=one holds the whole
income).
39
G
n y n
y y i j
j
n
i
n
1
2 1
1 1
_
( )
• A low Gini coefficient indicates
more equal income or wealth
distribution, while a high Gini
coefficient demonstrates more
unequal distribution.
สถานการณ์ความเหลื่อมล้้า
• World incomes are unequally distributed (inequality between
countries). In 2002:
– Pc per year income of richest country (Switzerland) (US$ 37930) 421 times
largest than poorest country (RD Congo) (US$ 90)
• Low and middle income countries produce 19.4% of world’s income;
they have around 85% of world’s pop
• Share of income of richest (poorest) countries more or less
unchanged since 1960. However:
– World distribution can be constant in relative terms but there has been lots of
change within the distribution.
– Ups as well as downs!
– Greatest mobility amongst middle-income countries
40
สถานการณ์ความเหลื่อมล้้า (cont.)
• Income distribution is also highly unequal within countries
– E. g. UK (1991): poorest 10% of population (lowest decile) gets 2.6% of all
national income; richest 10% of population (top decile) gets 27.3% of total
income
• There seems to be an inverted-U pattern in both between and
within country inequality (Kuznets):
• Low inequality amongst poor countries; high inequality amongst
middle income countries; low inequality amongst high income
countries
• For a given country: low inequality at low levels of economic
development; higher inequality in transition periods, lower
inequality at higher levels of development
41
ทฤษฎีและหลักฐานเชิงประจักษ์ว่าด้วยแนวโน้มระยะยาวของการ
กระจายรายได้
• ในการศึกษาแนวโน้มระยะยาวของการกระจายรายได้ สมมติฐานที่ได้รับการ
กล่าวขานกันมากที่สุดคือสมมติฐานของ Simon Kuznet ที่กล่าวว่าในระยะแรก
ของการพัฒนา ความเหลื่อมล้ าจะสูงขึ้นพร้อมกับการขยายตัวทางเศรษฐกิจ และ
เมื่อถึงระดับหนึ่งความเหลื่อมล้ าก็จะลดลง
42
Inequality
Income/Wealth/Time
รูปที่1 การเปลี่ยนแปลงของความเหลื่อมล้้าตามสมมติฐานของ Kuznet