part ii , item 7 in 2006 , cash provided by financing activities was $ 291 million which was primarily due to the proceeds from employee stock plans ( $ 442 million ) and an increase in debt of $ 1.5 billion partially offset by the repurchase of 17.99 million shares of schlumberger stock ( $ 1.07 billion ) and the payment of dividends to shareholders ( $ 568 million ) . schlumberger believes that at december 31 , 2006 , cash and short-term investments of $ 3.0 billion and available and unused credit facilities of $ 2.2 billion are sufficient to meet future business requirements for at least the next twelve months . summary of major contractual commitments ( stated in millions ) .
what is the ratio of the total debt to the purchase obligations
purchase obligations 2 $ 1526 $ 1490 $ 36 $ 2013 $ 2013 1 . excludes future payments for interest . includes amounts relating to the $ 1425 million of convertible debentures which are described in note 11 of the consolidated financial statements . 2 . represents an estimate of contractual obligations in the ordinary course of business . although these contractual obligations are considered enforceable and legally binding , the terms generally allow schlumberger the option to reschedule and adjust their requirements based on business needs prior to the delivery of goods . refer to note 4 of the consolidated financial statements for details regarding potential commitments associated with schlumberger 2019s prior business acquisitions . refer to note 20 of the consolidated financial statements for details regarding schlumberger 2019s pension and other postretirement benefit obligations . schlumberger has outstanding letters of credit/guarantees which relate to business performance bonds , custom/excise tax commitments , facility lease/rental obligations , etc . these were entered into in the ordinary course of business and are customary practices in the various countries where schlumberger operates . critical accounting policies and estimates the preparation of financial statements and related disclosures in conformity with accounting principles generally accepted in the united states requires schlumberger to make estimates and assumptions that affect the reported amounts of assets and liabilities , the disclosure of contingent assets and liabilities and the reported amounts of revenue and expenses . the following accounting policies involve 201ccritical accounting estimates 201d because they are particularly dependent on estimates and assumptions made by schlumberger about matters that are inherently uncertain . a summary of all of schlumberger 2019s significant accounting policies is included in note 2 to the consolidated financial statements . schlumberger bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances , the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources . actual results may differ from these estimates under different assumptions or conditions . multiclient seismic data the westerngeco segment capitalizes the costs associated with obtaining multiclient seismic data . the carrying value of the multiclient seismic data library at december 31 , 2006 , 2005 and 2004 was $ 227 million , $ 222 million and $ 347 million , respectively . such costs are charged to cost of goods sold and services based on the percentage of the total costs to the estimated total revenue that schlumberger expects to receive from the sales of such data . however , except as described below under 201cwesterngeco purchase accounting , 201d under no circumstance will an individual survey carry a net book value greater than a 4-year straight-lined amortized value. .