Apparently, the graph designer isn't familiar with the y vs. x convention. But that's not really the point (math errors annoy me, while grammatical ones don't for some reason). It seems that a linear plot isn't really appropriate. This graph and the one mk links appear to be biphasic more than anything. That is, there are a lot of countries bunched into two distinct groups. One in which the Gini coefficient is about 35 and GDP is uncorrelated to it; the other in which GDP is ~10k/capita and Gini is uncorrelated to it. It would be interesting to see if there are any qualitative distinctions between these countries. I don't think a linear regression yields any interesting data here, beyond that supply side doesn't work (which is a no brainer for anyone, well, with a brain).
The R^2 doesn't really knock your socks off, but there's something there. So that's 10x the Gini coefficient on bottom, and $GDP per capita on the left, I assume. I found this 2006 plot which looks similar.
He left off Singapore Hong Kong and Norway.
As well as all of Africa and most of south america What line of fit should one use for a l-shaped chart? Gini score seems to be non-correlated for the very poor countries and increasingly so for the richer ones. If Reganomics worked we would see high ginis correlating with high wealth this is not evident at all in the either chart.