Noted: Timothy Smeeding, a professor of public affairs and economics at the University of Wisconsin, has explored how the top quintile is pulling away from the rest of society. In an essay published earlier this year, “Gates, Gaps, and Intergenerational Mobility: The Importance of an Even Start,” Smeeding finds that the gap between the average income of households with children in the top quintile and households with children in the middle quintile has grown, in inflation-adjusted dollars, from $68,600 to $169,300 — that’s 147 percent.