the railroad collected approximately $ 18.8 billion and $ 16.3 billion of receivables during the years ended december 31 , 2011 and 2010 , respectively .upri used certain of these proceeds to purchase new receivables under the facility .the costs of the receivables securitization facility include interest , which will vary based on prevailing commercial paper rates , program fees paid to banks , commercial paper issuing costs , and fees for unused commitment availability .the costs of the receivables securitization facility are included in interest expense and were $ 4 million and $ 6 million for 2011 and 2010 , respectively .prior to adoption of the new accounting standard , the costs of the receivables securitization facility were included in other income and were $ 9 million for 2009 .the investors have no recourse to the railroad 2019s other assets , except for customary warranty and indemnity claims .creditors of the railroad do not have recourse to the assets of upri .in august 2011 , the receivables securitization facility was renewed for an additional 364-day period at comparable terms and conditions .contractual obligations and commercial commitments as described in the notes to the consolidated financial statements and as referenced in the tables below , we have contractual obligations and commercial commitments that may affect our financial condition .based on our assessment of the underlying provisions and circumstances of our contractual obligations and commercial commitments , including material sources of off-balance sheet and structured finance arrangements , other than the risks that we and other similarly situated companies face with respect to the condition of the capital markets ( as described in item 1a of part ii of this report ) , there is no known trend , demand , commitment , event , or uncertainty that is reasonably likely to occur that would have a material adverse effect on our consolidated results of operations , financial condition , or liquidity .in addition , our commercial obligations , financings , and commitments are customary transactions that are similar to those of other comparable corporations , particularly within the transportation industry .the following tables identify material obligations and commitments as of december 31 , 2011 : payments due by december 31 , contractual obligations after millions total 2012 2013 2014 2015 2016 2016 other .
[['contractual obligationsmillions', 'total', 'payments due by december 31 2012', 'payments due by december 31 2013', 'payments due by december 31 2014', 'payments due by december 31 2015', 'payments due by december 31 2016', 'payments due by december 31 after 2016', 'payments due by december 31 other'], ['debt [a]', '$ 12516', '$ 538', '$ 852', '$ 887', '$ 615', '$ 652', '$ 8972', '$ -'], ['operating leases [b]', '4528', '525', '489', '415', '372', '347', '2380', '-'], ['capital lease obligations [c]', '2559', '297', '269', '276', '276', '262', '1179', '-'], ['purchase obligations [d]', '5137', '2598', '568', '560', '276', '245', '858', '32'], ['other post retirement benefits [e]', '249', '26', '26', '26', '26', '26', '119', '-'], ['income tax contingencies [f]', '107', '31', '-', '-', '-', '-', '-', '76'], ['total contractualobligations', '$ 25096', '$ 4015', '$ 2204', '$ 2164', '$ 1565', '$ 1532', '$ 13508', '$ 108']]
[a] excludes capital lease obligations of $ 1874 million and unamortized discount of $ 364 million .includes an interest component of $ 5120 million .[b] includes leases for locomotives , freight cars , other equipment , and real estate .[c] represents total obligations , including interest component of $ 685 million .[d] purchase obligations include locomotive maintenance contracts ; purchase commitments for fuel purchases , locomotives , ties , ballast , and rail ; and agreements to purchase other goods and services .for amounts where we cannot reasonably estimate the year of settlement , they are reflected in the other column .[e] includes estimated other post retirement , medical , and life insurance payments and payments made under the unfunded pension plan for the next ten years .no amounts are included for funded pension obligations as no contributions are currently required .[f] future cash flows for income tax contingencies reflect the recorded liability for unrecognized tax benefits , including interest and penalties , as of december 31 , 2011 .where we can reasonably estimate the years in which these liabilities may be settled , this is shown in the table .for amounts where we cannot reasonably estimate the year of settlement , they are reflected in the other column. .

Question: what percentage of total material obligations and commitments as of december 31 , 2011 are operating leases?
Answer: 18%