Inequality: America's Great Destroyer

FORTUNE -- In making inequality a topic of Tuesday's State of the Union speech, President Obama did a lot more than address a phenomenon that undermines America's social cohesion and the effectiveness of its political process. He put on the national table an issue that is now attracting the interest of an increasing number of economists: Inequality is no longer just a consequence of a prolonged period of unbalanced (and, more recently, subpar) growth and high unemployment; it is also a growing contributor to disappointing economic performance.