39 annual report 2010 duke realty corporation | | related party transactions we provide property and asset management , leasing , construction and other tenant related services to unconsolidated companies in which we have equity interests . for the years ended december 31 , 2010 , 2009 and 2008 , respectively , we earned management fees of $ 7.6 million , $ 8.4 million and $ 7.8 million , leasing fees of $ 2.7 million , $ 4.2 million and $ 2.8 million and construction and development fees of $ 10.3 million , $ 10.2 million and $ 12.7 million from these companies . we recorded these fees based on contractual terms that approximate market rates for these types of services , and we have eliminated our ownership percentages of these fees in the consolidated financial statements . commitments and contingencies we have guaranteed the repayment of $ 95.4 million of economic development bonds issued by various municipalities in connection with certain commercial developments . we will be required to make payments under our guarantees to the extent that incremental taxes from specified developments are not sufficient to pay the bond debt service . management does not believe that it is probable that we will be required to make any significant payments in satisfaction of these guarantees . we also have guaranteed the repayment of secured and unsecured loans of six of our unconsolidated subsidiaries . at december 31 , 2010 , the maximum guarantee exposure for these loans was approximately $ 245.4 million . with the exception of the guarantee of the debt of 3630 peachtree joint venture , for which we recorded a contingent liability in 2009 of $ 36.3 million , management believes it probable that we will not be required to satisfy these guarantees . we lease certain land positions with terms extending to december 2080 , with a total obligation of $ 103.6 million . no payments on these ground leases are material in any individual year . we are subject to various legal proceedings and claims that arise in the ordinary course of business . in the opinion of management , the amount of any ultimate liability with respect to these actions will not materially affect our consolidated financial statements or results of operations . contractual obligations at december 31 , 2010 , we were subject to certain contractual payment obligations as described in the table below: .
( 1 ) our long-term debt consists of both secured and unsecured debt and includes both principal and interest . interest expense for variable rate debt was calculated using the interest rates as of december 31 , 2010 . ( 2 ) our unsecured lines of credit consist of an operating line of credit that matures february 2013 and the line of credit of a consolidated subsidiary that matures july 2011 . interest expense for our unsecured lines of credit was calculated using the most recent stated interest rates that were in effect . ( 3 ) our share of unconsolidated joint venture debt includes both principal and interest . interest expense for variable rate debt was calculated using the interest rate at december 31 , 2010 . ( 4 ) represents estimated remaining costs on the completion of owned development projects and third-party construction projects. .
Payments due by Period (in thousands)
Contractual Obligations Total 2011 2012 2013 2014 2015 Thereafter
Long-term debt (1) $5,413,606 $629,781 $548,966 $725,060 $498,912 $473,417 $2,537,470
Lines of credit (2) 214,225 28,046 9,604 176,575 - - -
Share of debt of unconsolidated joint ventures (3) 447,573 87,602 27,169 93,663 34,854 65,847 138,438
Ground leases 103,563 2,199 2,198 2,169 2,192 2,202 92,603
Operating leases 2,704 840 419 395 380 370 300
Development and construction backlog costs (4) 521,041 476,314 44,727 - - - -
Other 1,967 1,015 398 229 90 54 181
Total Contractual Obligations $6,704,679 $1,225,797 $633,481 $998,091 $536,428 $541,890 $2,768,992
contractual obligations payments due by period ( in thousands ) total payments due by period ( in thousands ) 2011 payments due by period ( in thousands ) 2012 payments due by period ( in thousands ) 2013 payments due by period ( in thousands ) 2014 payments due by period ( in thousands ) 2015 payments due by period ( in thousands ) thereafter
long-term debt ( 1 ) $ 5413606 $ 629781 $ 548966 $ 725060 $ 498912 $ 473417 $ 2537470
lines of credit ( 2 ) 214225 28046 9604 176575 - - -
share of debt of unconsolidated joint ventures ( 3 ) 447573 87602 27169 93663 34854 65847 138438
ground leases 103563 2199 2198 2169 2192 2202 92603
operating leases 2704 840 419 395 380 370 300
development and construction backlog costs ( 4 ) 521041 476314 44727 - - - -
other 1967 1015 398 229 90 54 181
total contractual obligations $ 6704679 $ 1225797 $ 633481 $ 998091 $ 536428 $ 541890 $ 2768992
what is the total long-term debt as a percentage of total contractual obligations?