Apparent conflicting data.
Wilmington's median or most common occurring household income (MHI) had fallen by 17%, from $34,880 in 2000 to $29,688 in 2013. Interesting to note the increasing degree of poverty in the city compared to the statewide $48,081 MHI.
The per capita or, average per person income, (PCI) rose by 9% from $17,346 in 2000 to $19,110 in 2013.
To me this data mimics the nation's widening income gap. The DHL departure and the recession did not take all of the wealth from the city it just changed hands.
Data source: http://www.city-data.com/city/Wilmington-Ohio.html