Joyce Appleby is an emeritus professor of history at UCLA and the author of "The Relentless Revolution: A History of Capitalism."

We hear a great deal these days about the top 1% and the bottom 99% in the American economic pyramid. But we also need to consider the 11%.

From 1776 to the present, the bottom 60% of the American population, as USC historian Carole Shammas has documented, has never had more than 11% of the country's wealth. We may embrace the American dream of broad prosperity and wealth equity, but we have never been close to achieving it.

There has been an explosion of studies examining inequality in the United States recently. They have been both illuminating and, at times, confusing. Sometimes people refer to the top 1% and bottom 99% using income, and at other times the studies look at wealth. Sometimes they have focused on individuals, sometimes on households, where there might by two or three earners.

Does it matter? Yes. Let's start with the difference between income and wealth. The top 1% of today's earners make more than $700,000 annually, and the top 1% in terms of wealth have assets of more than $9 million....