obligations is determined utilizing a cost build-up approach. The cost build-up approach determines fair value by estimating the costs related to fulfilling the obligations plus a normal profit margin. The estimated costs to fulfill the support obligations are based on the historical direct costs related to providing the support services and to correct any errors in the software products acquired. We do not include any costs associated with selling efforts or research and development or the related fulfillment margins on these costs. Profit associated with selling effort is excluded because the acquired entities would have concluded the selling effort on the support contracts prior to the acquisition date. The estimated research and development costs are not included in the fair value determination, as these costs are not deemed to represent a legal obligation at the time of acquisition. The sum of the costs and operating profit approximates, in theory, the amount that we would be required to pay a third party to assume the support obligation.

 

As a result, we did not recognize software license updates and product support revenues related to support contracts in the amount of $391 million and $320 million that would have been otherwise recorded by acquired businesses as independent entities in fiscal 2006 and 2005, respectively. Historically, substantially all of our customers, including customers from acquired companies, renew their contracts when the contract is eligible for renewal. To the extent these underlying support contracts are renewed, we will recognize the revenue for the full value of the support contracts over the support periods, the majority of which are one year. Had we included our estimated selling and research and development activities, and the associated margin for unspecified product upgrades and enhancements to be provided under our assumed support arrangements, the fair value of the support obligations would have been significantly higher than what we have recorded and we would have recorded a higher amount of software license updates and product support revenue historically and in future periods related to these assumed contracts.

Other significant estimates associated with the accounting for acquisitions include restructuring costs. Restructuring costs are primarily comprised of severance costs, costs of consolidating duplicate facilities and contract termination costs. Restructuring expenses are based upon plans that have been committed to by management but which are subject to refinement. To estimate restructuring expenses, management utilizes assumptions of the number of employees that would be involuntarily terminated and of future costs to operate and eventually vacate duplicate facilities. Estimated restructuring expenses may change as management executes the approved plan. Decreases to the cost estimates of executing the currently approved plans associated with pre-merger activities of the companies we acquire are recorded as an adjustment to goodwill indefinitely, whereas increases to the estimates are recorded as an adjustment to goodwill during the purchase price allocation period (generally within