Income inequality must have become a mainstream concern because even business leaders worry about it. A newly released survey by theHarvard Business School of its alumni about American competitiveness shows that a “troubling divergence in the American economy” could ultimately sink the country’s prospects. Even as large corporations, the wealthy, and “ highly skilled individuals” prosper, “middle-class and working-class citizens are struggling.” So are small businesses, which are an important source of new jobs. The result is a division of the U.S. into two parts, one small and wealthy, the other comprising the vast majority that finds it more difficult to get by as time moves on.