Annual report pursuant to Section 13 and 15(d)

Concentration of Rental Revenue

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Concentration of Rental Revenue
 12 Months Ended
Dec. 31, 2011
Concentration of Rental Revenue  
Concentration of Rental Revenue

4. Concentration of Rental Revenue

        We derived large concentrations of our revenue from real estate operations from certain tenants during the periods set forth in our consolidated statements of operations. The following table summarizes the percentage of our rental revenue (which excludes tenant recoveries and other real estate operations revenue) earned from (1) individual tenants that accounted for at least 5% of our rental revenue from continuing and discontinued operations and (2) the aggregate of the five tenants from which we recognized the most rental revenue in the respective years:

 
   For the Years Ended
December 31, 		 
 
   2011   2010   2009  

United States Government

     17 %   16 %   15 %

Northrop Grumman Corporation(1)

     8 %   9 %   8 %

Booz Allen Hamilton, Inc. 

     6 %   5 %   6 %

Five largest tenants

     38 %   35 %   34 %
(1)
Includes affiliated organizations and agencies and predecessor companies.

        We also derived in excess of 90% of our construction contract revenue from the United States Government in each of the years set forth on the consolidated statements of operations.

        In addition, we derived large concentrations of our total revenue from real estate operations (defined as the sum of rental revenue and tenant recoveries and other real estate operations revenue) from certain geographic regions. These concentrations are set forth in the segment information provided in Note 16. Several of these regions, including the Baltimore/Washington Corridor, Northern Virginia, Washington, DC—Capitol Riverfront, St. Mary's & King George Counties, Greater Baltimore, Maryland ("Greater Baltimore") and Suburban Maryland, are within close proximity to each other, and all but two of our regions with real estate operations (San Antonio, Texas ("San Antonio") and Colorado Springs, Colorado ("Colorado Springs")) are located in the Mid-Atlantic region of the United States.