Also be aware that the graph is a factually incorrect depiction of income. Towards the right end, up to about 80% it’s right, but the income curve takes a hockey-stick jump somewhere in the 90’s. At 95% the real curve is off this chart, and at 98% it’s well off the top of your computer screen.
If you read the article through to the end, the author states that it's an approximation. He also shows the actual IRS data graph, which does have that hockey stick at the end (as it would have to for a power law distribution).