It seems that both groups of authors agree that the poverty in SSA is on the decline, at least relatively speaking. When we take a broader measure of poverty ($2.00 a day) we see according to Ravallion and Chen that the decline went from 76.2% (1990), to 77.9% !(1996) to 73% (2005). When we assume a margin of al least 5% the decline does not look very impressive or stable or certain. The high level of poverty posses the question whether we really can speak about a possitive development. When we look at the absolute numbers we see an increase (as Ravallion correctly menstions). For SSA from 393.6 million in 1990, to 471.1 million (1996) to 556.7 milion (2005). That is an increase of 41% in absolute numbers since 1990. When we look at the mean consumption of the poorest of SSA (below $1.25) we see that their consumption has increased from 2002 to 2005 with about 1%. (What margin?) The average increase of the GDP per capita was 2.5%. (Margin?) All this taken together the conclusion based on theese numbers should be that absolute poverty is on the rise, and the relative poverty of the poorest compared with the average income is also on the rise. The other team of Columbia comes with the good news. However, we see that they used time series of PPPs, that they ignore the fundamentals of inequality and make use of GDP data that certainly cannot be trusted. Considering this it is not likely that their analysis can be called sound. The data limitations in Africa are such that each figure needs to be treated very carfully. Many figuers taken together even more carefully. It seems reasonable to assume that income is underestimated all over Africa. The more is earned the more will be underreported. Therefore the levels of poverty can be lower as estimated by Ravallion and Chen, the relative share of the poor may also be lower, the consumption may be higher but there is no reason to speak about a promising development. Fact is that we do not have data of sufficient quality to make strong statements. Assuming you have is fooling yourself. Moreover, the total fertility rate in Africa is not coming done rapidly enough (TFR is about 5). This means that behavior in Africa is not changing. That is bad news for the future. Since we cannot trust the economic data it is possible that we will face an increase of poverty in the coming years. Certainly in absolute numbers, possibly also relatively. Even if we do not have the tools to measure it.