Around 100 BC, a Roman nobleman calculated that it took about 100,000 sesterces a year to live comfortably. That was roughly 200 times the amount of money a poor city dweller needed to eke out a living. If an American needed the same multiple of the subsistence income to join the upper middle class today, the threshold would be $3.5 million. The United States economy has become less equal lately, but it remains much more egalitarian than the ancient Roman Republic.