The growing gap between the richest of the rich and the poorest of the poor has filled more space in national newspapers and airtime on political talk shows and sparked more studies among economists since the rapid rise and fall of the Occupy Wall Street movement in 2011. President Barack Obama made the issue of income inequality a centerpiece of his State of the Union address last month, calling for an increase in the minimum wage and an extension of unemployment benefits to help narrow the nation’s wealth disparity. But dispute remains among business leaders and worker advocates about whether income inequality is a real problem or simply capitalism at work.