On-Topic: Anything that good hackers would find interesting. That includes more than hacking and startups. If you had to reduce it to a sentence, the answer might be: anything that gratifies one's intellectual curiosity.[0]
It makes a good discussion piece, and while far from perfect, it does bring some interesting data to the table (such as the stagnation in poverty decline if you exclude China).
I think the article posited that the graphic was based on incomplete data and failed to show the effect of China's policies. He wasn't trying to make a case for it being all roses before 1981, he was trying to demonstrate that the Davos neo-liberals couldn't claim to be right.
Perhaps it's suitable for HN because it raises the question of good data analysis versus making up numbers that amount to false news.