14 million Americans live in extremely poor neighborhoods
    Nearly 14 million Americans live in extremely poor neighborhoods, more than twice as many as in 2000.   The economic downturn in the early 2000s, which was  followed by slow job growth and then the Great Recession, sent the  poverty rate soaring. The growing concentration of poverty is closely  linked to the availability of affordable housing, the report from  Brookings Institution's Metropolitan Policy Program found.     In 2000, there were just over 2,000 Census tracts with concentrated rates of poverty   -- where 40% or more of residents are poor. in the period between 2010  and 2014, that number had grown to nearly 4,200. Brookings compared data  from the 2000 decennial Census and from the American Community Survey  that looked at 2010 through 2014.   Poverty often becomes  concentrated in neighborhoods with blocks of public or subsidized  housing. Also, it can happen when middle income families move away,  leaving the poor behind, said study co-author Elizabeth Kneebone, a...