Over the decades when the richest Americans took wealth and income away from the non-rich 90%, forcing them down into poverty, the intermediate group of not-quite-rich (around 10%) have maintained their comfortable status by building barriers to social mobility between them and the 90%.

The article refers to the "9.9%", but that is unwarranted precision. The line between that group and the 90% is not a sharp one; we cannot say whether they are 10%, 9.9%, or 10.1% of the population.

The article's terminology is slightly skewed from historical precedent. The term "aristocracy" should refer to the richest .1%. The proper term for the comfortable 10% is "gentry".