WASHINGTON — The American suburb is no longer a refuge from poverty in cities. A pair of analyses by the nonprofit Brookings Institution paints a bleak economic picture for the 100 largest metropolitan areas over the past decade and in coming years, and finds that suburbs now are home to one-third of the nation's poor, and rising. The study of census data finds that since 2000, the number of poor people in the suburbs jumped by 37.4 percent to 13.7 million.