Odd. they list New Jersey, Pennsylvania, and New York as having among the highest outbound proportions. They also list Delaware as not being mid-Atlantic. Then they say that the Mid-Atlantic has the highest inbound proportion. These states make up the Mid-Atlantic states!
(Some people regard Maryland as Mid-Atlantic, others regard it as having been a southern colony, along with VA, NC, SC, and GA.)
Geographic illiteracy on the part of the author, who just looked at a map and decided that states midway down the US Atlantic coast were “Mid-Atlantic.”