“I have a dream,” declared Martin Luther King, in a speech that has lost none of its power to inspire. And some of that dream has come true. When King spoke in the summer of 1963, America was a nation that denied basic rights to millions of its citizens, simply because their skin was the wrong color. Today racism is no longer embedded in law. And while it has by no means been banished from the hearts of men, its grip is far weaker than once it was.

To say the obvious: to look at a photo of President Obama with his cabinet is to see a degree of racial openness — and openness to women, too — that would have seemed almost inconceivable in 1963. When we observe Martin Luther King’s Birthday, we have something very real to celebrate: the civil rights movement was one of America’s finest hours, and it made us a nation truer to its own ideals.

Yet if King could see America now, I believe that he would be disappointed, and feel that his work was nowhere near done. He dreamed of a nation in which his children “will not be judged by the color of their skin but by the content of their character.” But what we actually became is a nation that judges people not by the color of their skin — or at least not as much as in the past — but by the size of their paychecks. And in America, more than in most other wealthy nations, the size of your paycheck is strongly correlated with the size of your father’s paycheck.

Goodbye Jim Crow, hello class system.

Economic inequality isn’t inherently a racial issue, and rising inequality would be disturbing even if there weren’t a racial dimension. But American society being what it is, there are racial implications to the way our incomes have been pulling apart. And in any case, King — who was campaigning for higher wages when he was assassinated — would surely have considered soaring inequality an evil to be opposed.