This discussion was held on the underlying Planet Money article [1] [2]
The problem then, and the problem now, is that this is arbitrarily defining middle class. Can't we just call this a boxplot[3] of income in major cities, and not make this into a discussion of what "middle class means"?
Exactly - in a well connected world/economy, local measurements of income don't mean much. As someone that's lived in and near Detroit, the incomes listed there have no relation to my idea of what's lower/middle/upper class. Most people in the area would probably peg those closer to what you see on Dallas or San Diego's charts. Detroit proper (as opposed to the sprawling Detroit area, which mostly looks like any suburban metro area) is simply a very poor city - I doubt it's much comfort to anyone making $30,000 there that they happen to fall in the middle, and I doubt that an employer would have any luck trying to pay an engineer a $60,000 "upper class" salary.
The problem then, and the problem now, is that this is arbitrarily defining middle class. Can't we just call this a boxplot[3] of income in major cities, and not make this into a discussion of what "middle class means"?
[1] https://news.ycombinator.com/item?id=9237345 [2] http://www.npr.org/blogs/money/2015/03/19/394057221/how-much... [3] https://en.wikipedia.org/wiki/Box_plot