inputs and assumptions, including: (1) the expected number of miles awarded and number of miles redeemed, (2) the rate at which we sell mileage credits to other airlines, (3) published rates on our website for baggage fees, discounted access to Delta Sky Club lounges and other benefits while traveling on Delta and (4) brand value. The impact of adopting the relative selling price method re-allocated a portion of the embedded discount to the travel component, lowering the deferral rate we use to record miles sold under the agreements and increasing revenue recognized on the remaining deliverables.

We recognize revenue as we deliver each sales element. We defer the travel deliverable (mileage credits) as part of frequent flyer deferred revenue and recognize passenger revenue as the mileage credits are used for travel. The revenue allocated to the remaining deliverables is recorded in other revenue. We recognize the revenue for these services as they are performed.

Breakage. For mileage credits that we estimate are not likely to be redeemed (“breakage”), we recognize the associated value proportionally during the period in which the remaining mileage credits are expected to be redeemed. Management uses statistical models to estimate breakage based on historical redemption patterns. A change in assumptions as to the period over which mileage credits are expected to be redeemed, the actual redemption activity for mileage credits or the estimated fair value of mileage credits expected to be redeemed could have a material impact on our revenue in the year in which the change occurs and in future years. At December 31, 2015 , the aggregate deferred revenue balance associated with the SkyMiles Program was $3.9 billion . A hypothetical 1% change in the number of outstanding miles estimated to be redeemed would result in a $29 million impact on our deferred revenue liability at December 31, 2015 .

Goodwill and Indefinite-Lived Intangible Assets

We apply a fair value-based impairment test to the carrying value of goodwill and indefinite-lived intangible assets 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 indefinitelived 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