At first I was impressed that Charles and Jason found so much to agree on. (I don't think I would have been as successful with either.) But on closer inspection, it seems that they only agree on the obvious, and ignore some less obvious things that really matter. Tweets follow.
One key point they make is that we find less progress against global poverty at higher poverty lines. At some point, progress in reducing either the % poor or number of poor comes close to zero. This is surely pretty obvious; no numbers are needed. (Sketch of proof follows.)
[Note: Define rate of poverty reduction (RPR) as the annual change in % in poverty. Suppose that all incomes grow over time. Then RPR>0 whatever the line (z), but there will always be some z above which the RPR tends to fall as z rises. For high enough z, RPR is close to zero.]
But surely we care most about gains to the poorest. Sure, $1.90 a day (2011 prices) is a low line (historically anchored to poorest countries). But you can also go lower. Then it is not obvious what we will find. Next (last) tweet gives my answer.
The numbers tell me that we have seen very little progress for the world's poorest, i.e., the floor is not rising. (Figure gives floor in 2005 prices; it is about $1.00 in 2011 prices.) That is much less obvious, and surely much more worrying.
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