The US Census Bureau defines lower class as the lowest 20% of incomes.
Pew defines it as the lowest 2/3 of the median.
If the highest income is $100, 20% is $20.
At 2/3 the median, if the median is $30, lower-class is $20.
Is there a reason they’re tying income classes to people within those classes, and not what it costs to survive within the economy?
Or maybe there are laws or regulations that would be triggered if you move the goal post. If you start reporting the number of poor people or their income in a different way, that could affect government spending. If that’s the case, there could be a lot of friction in trying to update the calculations.