These are states (plus the District of Columbia) where the annual growth rate in the recession years 2007 to 2009 was greater than in the prosperity years of 2003 to 2007. All have been characterized during the decade by large immigration inflow and large domestic migration outflow...
...the availability of high welfare benefits in these states may be one of their attractions for many immigrants; in 2008 to 2009, high welfare benefits accounted for 42 percent of the nation’s entire immigrant inflow.
Link: <http://www.american.com/archive/2010/february/how-the-recession-has-changed-american-migration>
What "welfare" are they talking about, I wonder.