A new NBER working paper African Poverty is Falling…Much Faster than You Think! from economists Xavier Sala-i-Martin and Maxim Pinkovskiy argues that African poverty has been rapidly falling across Africa since 1995. They use methods they use to look at global income distributions to show that recent economic growth has reduced rather than enhanced Africa’s huge levels of inequality.
Figure 5 from "African Poverty is Falling...Much Faster than You Think" NBER 2010
These kinds of graphs tend to be about $ income. This is different to poverty – a subsistence farmer can be living quite well.
These previous post discuss rising non income based measures of wellbeing, most of which seem to be strongly correlated to the human development index.
http://rs.resalliance.org/2006/11/12/human-development-canada-and-water/
http://rs.resalliance.org/2005/07/13/well-being-vs-wealth-1-quality-of-life/