For anyone who's wondering who the author is: Chris Arnade got a Ph.D. in particle physics at Johns Hopkins University, and then worked for 20 years as a bond trader on Wall Street. In 2011, he became interested in social class in the US -- what he calls the distinction between "front-row kids" and "back-row kids."

So he became a sort of itinerant photographer/journalist, documenting the lives of poor or middle-class people in unglamorous places -- often Rust Belt towns.

Wikipedia: https://en.wikipedia.org/wiki/Chris_Arnade

Thanks for putting those together and commenting, I may have missed that connection on my own.

I think his McDonalds test is particularly interesting, and while it probably has some holes, I think it has some merit as at least a leading indicator of which group you're a part.