"D.C.'s median household income was only slightly higher than the national average in 2006. But by 2015 it was almost 40% higher" Isn't this just another way o

"D.C.'s median household income was only slightly higher than the national average in 2006. But by 2015 it was almost 40% higher" Isn't this just another way of saying D.C. is defined to be a highly urbanized area?