“They define the ‘size’ of the middle class as the fraction of people whose income is between 75% and 200% of the median income.”

It is also worth mentioning that the current median annual income for an individual in the U.S. is, in round numbers, $28,000 — before any taxes. That in itself is hardly enough income to have ‘enough’, much less any more than sufficiency, especially in an urban area — where most of the jobs — and the highest taxes (property and sales) — are. Seventy-five percent of that would be $21,000 (before any taxes), which is not enough for food,clothing, a home (including utilities), and transportation anywhere. To work full-time in this country earning the Federal minimum wage is to live in poverty.