customary affirmative and negative covenants and events of default for an unsecured financing arrangement , including , among other things , limitations on consolidations , mergers and sales of assets . financial covenants include a maximum leverage ratio of 3.0 to 1.0 and a minimum interest coverage ratio of 3.5 to 1.0 . if we fall below an investment grade credit rating , additional restrictions would result , including restrictions on investments , payment of dividends and stock repurchases . we were in compliance with all covenants under the senior credit facility as of december 31 , 2007 . commitments under the senior credit facility are subject to certain fees , including a facility and a utilization fee . the senior credit facility is rated a- by standard & poor 2019s ratings services and is not rated by moody 2019s investors 2019 service , inc . we also have available uncommitted credit facilities totaling $ 70.4 million . management believes that cash flows from operations , together with available borrowings under the senior credit facility , are sufficient to meet our expected working capital , capital expenditure and debt service needs . should investment opportunities arise , we believe that our earnings , balance sheet and cash flows will allow us to obtain additional capital , if necessary . contractual obligations we have entered into contracts with various third parties in the normal course of business which will require future payments . the following table illustrates our contractual obligations ( in millions ) : contractual obligations total 2008 thereafter .
what percentage of total contractual obligations is operating leases?
total contractual obligations $ 591.6 $ 58.6 $ 156.4 $ 203.9 $ 172.7 critical accounting estimates our financial results are affected by the selection and application of accounting policies and methods . significant accounting policies which require management 2019s judgment are discussed below . excess inventory and instruments 2013 we must determine as of each balance sheet date how much , if any , of our inventory may ultimately prove to be unsaleable or unsaleable at our carrying cost . similarly , we must also determine if instruments on hand will be put to productive use or remain undeployed as a result of excess supply . reserves are established to effectively adjust inventory and instruments to net realizable value . to determine the appropriate level of reserves , we evaluate current stock levels in relation to historical and expected patterns of demand for all of our products and instrument systems and components . the basis for the determination is generally the same for all inventory and instrument items and categories except for work-in-progress inventory , which is recorded at cost . obsolete or discontinued items are generally destroyed and completely written off . management evaluates the need for changes to valuation reserves based on market conditions , competitive offerings and other factors on a regular basis . income taxes fffd we estimate income tax expense and income tax liabilities and assets by taxable jurisdiction . realization of deferred tax assets in each taxable jurisdiction is dependent on our ability to generate future taxable income sufficient to realize the benefits . we evaluate deferred tax assets on an ongoing basis and provide valuation allowances if it is determined to be 201cmore likely than not 201d that the deferred tax benefit will not be realized . federal income taxes are provided on the portion of the income of foreign subsidiaries that is expected to be remitted to the u.s . we operate within numerous taxing jurisdictions . we are subject to regulatory review or audit in virtually all of those jurisdictions and those reviews and audits may require extended periods of time to resolve . we make use of all available information and make reasoned judgments regarding matters requiring interpretation in establishing tax expense , liabilities and reserves . we believe adequate provisions exist for income taxes for all periods and jurisdictions subject to review or audit . commitments and contingencies 2013 accruals for product liability and other claims are established with internal and external legal counsel based on current information and historical settlement information for claims , related fees and for claims incurred but not reported . we use an actuarial model to assist management in determining an appropriate level of accruals for product liability claims . historical patterns of claim loss development over time are statistically analyzed to arrive at factors which are then applied to loss estimates in the actuarial model . the amounts established equate to less than 5 percent of total liabilities and represent management 2019s best estimate of the ultimate costs that we will incur under the various contingencies . goodwill and intangible assets 2013 we evaluate the carrying value of goodwill and indefinite life intangible assets annually , or whenever events or circumstances indicate the carrying value may not be recoverable . we evaluate the carrying value of finite life intangible assets whenever events or circumstances indicate the carrying value may not be recoverable . significant assumptions are required to estimate the fair value of goodwill and intangible assets , most notably estimated future cash flows generated by these assets . as such , these fair valuation measurements use significant unobservable inputs as defined under statement of financial accounting standards no . 157 , fair value measurements . changes to these assumptions could require us to record impairment charges on these assets . share-based payment 2013 we account for share-based payment expense in accordance with the fair value z i m m e r h o l d i n g s , i n c . 2 0 0 7 f o r m 1 0 - k a n n u a l r e p o r t .