With rents rising and incomes shrinking across the country, the Chicago-area has fallen behind other major metropolitan areas in creating new housing for its poorest families during the past decade. But why? It’s a question that jumped out at us while checking out some interesting new research by a Washington D.C.-based think-tank, the Urban Institute. We were using this interactive map to see how Cook County stacks up with other big cities when it comes to matching “extremely low-income” households with rentals they can actually afford. In Cook County, which is anchored by Chicago, the number of households that fit the extreme poverty status (that means a household of four is getting by on $22,750 or less each year, according to the U.S. Department of Housing and Urban Development) hasn’t exactly grown by leaps and bounds since 2000.