in november 2016 , we issued $ 45 million of fixed rate term notes in two tranches to two insurance companies . principal payments commence in 2023 and 2028 and the notes mature in 2029 and 2034 , respectively . the notes carry interest rates of 2.87 and 3.10 , respectively . we used proceeds of the notes to pay down borrowings under our revolving credit facility . in january 2015 , we issued $ 75 million of fixed rate term notes to an insurance company . principal payments commence in 2020 and the notes mature in 2030 . the notes carry an interest rate of 3.52 percent . we used proceeds of the notes to pay down borrowings under our revolving credit facility . at december 31 , 2016 , we had available borrowing capacity of $ 310.8 million under this facility . we believe that the combination of cash , available borrowing capacity and operating cash flow will provide sufficient funds to finance our existing operations for the foreseeable future . our total debt increased to $ 323.6 million at december 31 , 2016 compared with $ 249.0 million at december 31 , 2015 , as our cash flows generated in the u.s were more than offset by our share repurchase activity and our purchase of aquasana . as a result , our leverage , as measured by the ratio of total debt to total capitalization , was 17.6 percent at the end of 2016 compared with 14.7 percent at the end of 2015 . our u.s . pension plan continues to meet all funding requirements under erisa regulations . we were not required to make a contribution to our pension plan in 2016 but made a voluntary $ 30 million contribution due to escalating pension benefit guaranty corporation insurance premiums . we forecast that we will not be required to make a contribution to the plan in 2017 and we do not plan to make any voluntary contributions in 2017 . for further information on our pension plans , see note 10 of the notes to consolidated financial statements . during 2016 , our board of directors authorized the purchase of an additional 3000000 shares of our common stock . in 2016 , we repurchased 3273109 shares at an average price of $ 41.30 per share and a total cost of $ 135.2 million . a total of 4906403 shares remained on the existing repurchase authorization at december 31 , 2016 . depending on factors such as stock price , working capital requirements and alternative investment opportunities , such as acquisitions , we expect to spend approximately $ 135 million on share repurchase activity in 2017 using a 10b5-1 repurchase plan . in addition , we may opportunistically repurchase an additional $ 65 million of our shares in 2017 . we have paid dividends for 77 consecutive years with payments increasing each of the last 25 years . we paid dividends of $ 0.48 per share in 2016 compared with $ 0.38 per share in 2015 . in january 2017 , we increased our dividend by 17 percent and anticipate paying dividends of $ 0.56 per share in 2017 . aggregate contractual obligations a summary of our contractual obligations as of december 31 , 2016 , is as follows: .
what percentage of total aggregate contractual obligations is due to pension and post-retirement obligations?
as of december 31 , 2016 , our liability for uncertain income tax positions was $ 4.2 million . due to the high degree of uncertainty regarding timing of potential future cash flows associated with these liabilities , we are unable to make a reasonably reliable estimate of the amount and period in which these liabilities might be paid . we utilize blanket purchase orders to communicate expected annual requirements to many of our suppliers . requirements under blanket purchase orders generally do not become committed until several weeks prior to our scheduled unit production . the purchase obligation amount presented above represents the value of commitments that we consider firm . recent accounting pronouncements refer to recent accounting pronouncements in note 1 of notes to consolidated financial statements. .