Households. The original source is derived from IRS tax return data. It's compiled by the Congressional Budget Office.
However, they aren't my charts. I just happened to encounter them in a search, and found them very useful. You can find the entire set, and the source data, here:
As they are for households, then they suffer from exactly the artifact exposed by the article. Individual income inequality has changed hardly at all. Household inequality has changed a bit because of what I, if I may, term the “Bell Curve Effect”.