More people left Phoenix in 2009 than came. The map above visualizes moves to and from Phoenix; counties that took more migrants than they sent are linked with red lines. Counties that sent more migrants than they took are linked with blue lines.
I've sent this link out before, but Forbes now has four articles attached to interactive mapping tool that analyze the data (including one by geographer Michael Conzen). Also the new data has been added and the visualization has also been improved...very cool features with tremendous amounts of teaching applications.
Via Seth Dixon