"In The Size of the Economy and the Distribution of Income in the Roman Empire, a careful paper published in the Journal of Roman Studies in 2009, Walter Scheidel and Steven Friesen estimate the size and distribution of the Roman economy at its demographic peak around the middle of the 2nd century c.e.
We conclude that in the Roman Empire as a whole, a ‘middling’ sector of somewhere around 6 to 12 per centat http://marginalrevolution.com/marginalrevolution/2011/12/roman-empire-more-equal-than-the-united-states.html
of the population, defined by a real income of between 2.4 and 10 times ‘bare bones’
subsistence or 1 to 4 times ‘respectable’ consumption levels, would have occupied a fairly
narrow middle ground between an élite segment of perhaps 1.5 per cent of the population and a vast majority close to subsistence level of around 90 per cent. In this system, some 1.5 per cent of households controlled 15 to 25 per cent of total income, while close to
10 per cent took in another 15 to 25 per cent, leaving not much more than half of all income for all remaining households..."
