56 / 57 management 2019s discussion and analysis of financial condition and results of operations junior subordinate deferrable interest debentures in june 2005 , we issued $ 100.0 a0million of trust preferred securities , which are reflected on the balance sheet as junior subordinate deferrable interest debentures . the proceeds were used to repay our revolving credit facility . the $ 100.0 a0million of junior subordi- nate deferrable interest debentures have a 30-year term ending july 2035 . they bear interest at a fixed rate of 5.61% ( 5.61 % ) for the first 10 years ending july 2015 . thereafter , the rate will float at three month libor plus 1.25% ( 1.25 % ) . the securities are redeemable at par . restrictive covenants the terms of the 2011 revolving credit facility and certain of our senior unsecured notes include certain restrictions and covenants which may limit , among other things , our ability to pay dividends ( as discussed below ) , make certain types of investments , incur additional indebtedness , incur liens and enter into negative pledge agreements and the disposition of assets , and which require compliance with financial ratios including our minimum tangible net worth , a maximum ratio of total indebtedness to total asset value , a minimum ratio of ebitda to fixed charges and a maximum ratio of unsecured indebtedness to unencumbered asset value . the dividend restriction referred to above provides that we will not during any time when we are in default , make distributions with respect to common stock or other equity interests , except to enable us to continue to qualify as a reit for federal income tax purposes . as of december a031 , 2011 and 2010 , we were in compli- ance with all such covenants . market rate risk we are exposed to changes in interest rates primarily from our floating rate borrowing arrangements . we use interest rate deriv- ative instruments to manage exposure to interest rate changes . a a0hypothetical 100 a0basis point increase in interest rates along the entire interest rate curve for 2011 and 2010 , would increase our annual interest cost by approximately $ 12.3 a0million and $ 11.0 a0mil- lion and would increase our share of joint venture annual interest cost by approximately $ 4.8 a0million and $ 6.7 a0million , respectively . we recognize all derivatives on the balance sheet at fair value . derivatives that are not hedges must be adjusted to fair value through income . if a derivative is a hedge , depending on the nature of the hedge , changes in the fair value of the derivative will either be offset against the change in fair value of the hedged asset , liability , or firm commitment through earnings , or recognized in other comprehensive income until the hedged item is recognized in earnings . the ineffective portion of a derivative 2019s change in fair value is recognized immediately in earnings . approximately $ 4.8 a0billion of our long- term debt bore interest a0at fixed rates , and therefore the fair value of these instru- ments is affected by changes in the market interest rates . the interest rate on our variable rate debt and joint venture debt as of december a031 , 2011 ranged from libor plus 150 a0basis points to libor plus 350 a0basis points . contractual obligations combined aggregate principal maturities of mortgages and other loans payable , our 2011 revolving credit facility , senior unsecured notes ( net of discount ) , trust preferred securities , our share of joint venture debt , including as- of-right extension options , estimated interest expense ( based on weighted average interest rates for the quarter ) , and our obligations under our capital lease and ground leases , as of december a031 , 2011 are as follows ( in thousands ) : .

Table: 2012 2013 2014 2015 2016 thereafter total property mortgages $ 52443 $ 568649 $ 647776 $ 270382 $ 556400 $ 2278190 $ 4373840 revolving credit facility 2014 2014 2014 2014 350000 2014 350000 trust preferred securities 2014 2014 2014 2014 2014 100000 100000 senior unsecured notes 119423 2014 98578 657 274804 777194 1270656 capital lease 1555 1555 1555 1592 1707 42351 50315 ground leases 33429 33429 33429 33429 33533 615450 782699 estimated interest expense 312672 309280 269286 244709 212328 470359 1818634 joint venture debt 176457 93683 123983 102476 527814 800102 1824515 total $ 695979 $ 1006596 $ 1174607 $ 653245 $ 1956586 $ 5083646 $ 10570659

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Question: a hypothetical 100 basis point increase in interest rates along the entire interest rate curve for 2011 and 2010 would increase our annual interest cost by what average amount , in millions?
Answer: 11.6
Calculation: divide(add(12.3, 11.0), const_2)