Only 16 percent of District homeowners were under water on their mortgages by the end of 2009, compared to a U.S. average of nearly 23.8 percent, according to the fourth quarter report released by FirstAmerican CoreLogic last week [.PDF]. That’s roughly a third less than the national average. While that alone may not having you cheering, it’s probably worth a dignified fist bump for the embattled home owner set. Another 4.5 percent are near negative…