It _is_ incredibly positive how the world economic system has been improving poverty in some of the most impoverished areas in the world. However, I don't think we can look at an average number and ignore concerns at the top end of the curve where many life quality measures and wealth accumulation have been going backwards.

The world economy isn't homogeneous, and what we may be looking at is that the current system is pretty good at taking people in economic/industrialized state A -> B, but bad at going from B -> C. If that's the case, sooner or later more and more people will arrive at state B and we will have a problem. It's even more of a problem if we get to B and it has people slipping back to state A in life qualitative measures (irrespective of imperfect quantitative measures like GDP...).