on an annual basis (as of October 1) and, if certain events or circumstances indicate that an impairment loss may have been incurred, on an interim basis. We assess the value of our goodwill and indefinite-lived assets under either a qualitative or quantitative approach. Under a qualitative approach, we consider various market factors, including the key assumptions listed below. We analyze these factors to determine if events and circumstances have affected the fair value of goodwill and indefinite-lived intangible assets. If we determine that it is more likely than not that the asset may be impaired, we use the quantitative approach to assess the asset's fair value and the amount of the impairment. Under a quantitative approach, we calculate the fair value of the asset using the key assumptions listed below. If the asset's carrying value exceeds its fair value calculated using the quantitative approach, we will record an impairment charge for the difference in fair value and carrying value.  

 

When we evaluate goodwill for impairment using a quantitative approach, we estimate the fair value of the reporting unit by considering market capitalization and other factors. When we perform a quantitative impairment assessment of our indefinite-lived intangible assets, fair value is estimated based on (1) recent market transactions, where available, (2) a combination of limited market transactions and the lease savings method for certain airport slots (which reflects potential lease savings from owning the slots rather than leasing them from another airline at market rates), (3) the royalty method for the Delta tradename (which assumes hypothetical royalties generated from using our tradename) or (4) projected discounted future cash flows (an income approach).  

 

Key Assumptions. The key assumptions in our impairment tests include: (1) forecasted revenues, expenses and cash flows, (2) terminal period revenue growth and cash flows, (3) an estimated weighted average cost of capital, (4) assumed discount rates depending on the asset and (5) a tax rate. These assumptions are consistent with those hypothetical market participants would use. Since we are required to make estimates and assumptions when evaluating goodwill and indefinite-lived intangible assets for impairment, actual transaction amounts may differ materially from these estimates. In addition, we consider the amount by which the intangible assets' fair value exceeded their carrying value in the most recent fair value measurement calculated using a quantitative approach.  

 

Changes in certain events and circumstances could result in impairment. Factors which could cause impairment include, but are not limited to, (1) negative trends in our market capitalization, (2) reduced profitability resulting from lower passenger mile yields or higher input costs (primarily related to fuel and employees), (3) lower passenger demand as a result of weakened U.S. and global economies, (4) interruption to our operations due to a prolonged employee strike, terrorist attack, or other reasons, (5) changes to the regulatory environment (e.g., diminished slot restrictions or additional Open Skies