The [Pew Research article they linked to](https://www.pewresearch.org/fact-tank/2018/09/06/the-american-middle-class-is-stable-in-size-but-losing-ground-financi

The [Pew Research article they linked to](https://www.pewresearch.org/fact-tank/2018/09/06/the-american-middle-class-is-stable-in-size-but-losing-ground-financially-to-upper-income-families/ https://www.pewresearch.org/fact-tank/2018/09/06/the-america...) uses this definition: > In our analysis, “middle-income” Americans are adults whose annual household income is two-thirds to double the national median, after incomes have been adjusted for household size. And they seem to use "middle-income" and "middle-class" interchangeably. Note that this definition is quite different than what may have been used in your history/economics classes in school/college.