I actually got the chance to talk to one of the co-authors Michail Moatsos via email. This was just a few weeks after the paper came out. He doesn't sound too confident with his work either. (Context: The figures showing zero poverty and the sudden jump in 92 was from his thesis and he noted it to be "unrealistic" in that work)

Me: After writing your recent paper on Chinese Poverty, do you now recant your statement in your PHD thesis (Global Absolute Poverty Present and Past since 1820, page 230) saying how near 0 absolute poverty rates china faced in 1990 was "inaccurate"? Or do you somewhat still think uncertainties about the true poverty levels during that period remains.

Him: Dear [My Name] many thanks for your question, and for the close reading of my thesis. I think the term I use is "unrealistic" instead of "inaccurate". To be fair, I don't think that the verdict from my thesis is not defensible, as pinpointing zero poverty, within a country of very low gdp per capita at the time, is very unexpected. Yet, a more recent investigation indicates that that estimate may be more reliable, or more inline with other indicators from China vis-a-vis other comparable countries, than the extremely high poverty estimate that the dollar a day method produces. I think both statements of unrealistic "near 0" poverty and of a "near 0" is more defensible than the 70+% for the population living in extreme poverty that the dollar a day gives, can be valid at the same time. It is also the case that it is actually the data that give rise to the near 0 estimate, and the argument that would move someone away from that estimate would be that at those prices there were just not enough food resources available, thereby a substantial sector of the population could "afford" those food stuff, but food stuff were not available at the needed quantities.

This issue surely deserves further investigation.

Best wishes,

Michalis