Don't these definitions have a more solid statistical economic meaning here? As in: middle "class" is the middle quintile of income. This makes the other strata

Don't these definitions have a more solid statistical economic meaning here? As in: middle "class" is the middle quintile of income. This makes the other strata fall pretty reasonably too: 80%-100%: Ruling Class 60-80%: Upper Class 40-60%: Middle Class 20-40%: Working Class 0-20%: Lower Class