Sure it's objective in the mathematical sense, but if you have 2 kids and two people working with a combined income of 112k you'd be upper class? I feel like a better way of looking at it would be average household income/average area COL per person or something, right?

Additionally, if the wealth distribution curve for the country is basically a backwards "L" with the bend at the ~99th percentile, the difference between the 60th and 80th percentiles isn't really meaningful since the "upper class" is clearly the 99th percentile.

Edit: obviously there are also social caste connotations that used to be applied here too, but I'm only interested in the economic definition.