I find the plots of distribution of global income here very illuminating - https://www.gapminder.org/income-mountains-dataset-v2/

Because the nicely shaped bell curves used in TFA are not at all what the distribution actually looks like. There is a significant right-skew. Don't miss the log-scale on x-axis in the first few graphs as well.

The distributions in TFA are accurate. Compare with the shape of the 2015 distribution here: https://ourworldindata.org/the-history-of-global-economic-in...