Table 10. Summary Results of Income Distribution by Income Levels,
1990 -2007 (or latest available) in PPP constant 2005 international dollars*
Low-income Middle-income High-income
1990 2000 2007 1990 2000 2007 1990 2000 2007
Q5 47.1 46.5 48.1 64.9 58.0 55.2 44.2 45.4 44.4
Q4 21.3 21.9 22.4 16.4 19.9 20.6 23.5 23.0 22.9
Q3 14.7 14.8 14.1 9. 4 11.2 12.2 16.0 15.7 16.0
Q2 10.5 10.4 10.5 5.9 7.0 7.4 10.8 10.5 11.2
Q1 6.3 6.4 4.9 3.4 4.0 4.7 5.5 5.3 5.4

of observations 31 26 17 49 70 74 33 31 31

% of global pop. 4.8 7.9 9.9 66.1 69.3 69.0 15.2 14.0 13.5
% of global GDP 0.6 0.8 1.0 29.7 32. 0 38.5 55.0 54.5 49.1
% of sample 5.6 8.6 10.7 76.8 76.0 74.7 17.7 15.4 14.6
% of sample GDP 0.7 1.0 1.2 34.8 36.7 43.4 64.5 62.4 55.4
Source: Authors’ calculations using World Bank (2011), UNU-WIDER (2008) and Eurostat (2011)

• According to the global accounting model

While most of middle-income countries increased inequality in

recent years, it is important to note that middle classes and—to a

lesser extent—poorer-income groups seem to be getting an

increasing share of income in recent years. This advance is still

vulnerable and needs to be quickly accelerated in the 21st century

(Ravallion 2009).

Middle classes and poorer-income groups appear to be doing worse

in both low- and high- income countries—for the benefit of the

richest quintile. This has generated debate on how states need to

meet the welfare needs of all of their citizens, including the middle

classes who are critical for nation building (Birdsall 2010). From an

equity point of view, what is clear is that growth and development

should not only be “pro-rich,” as it tends to be now, but ensure

equitable outcomes for all. For lower-income countries, this implies

evolving from “poverty reduction” to “inclusive development”

(Deacon 2010).

2.F. Alternative metrics: Wealth distribution

It is important to note that income inequality measures, which are

often based on household consumption, do not capture other

household wealth, such as financial assets, real estate and savings

instruments that high-income groups commonly possess. Some

recent studies do include metrics for wealth, and they offer an even