value for indefinite-lived assets, and then we apply an asset-specific discount rate to arrive at a net present value amount. Some of the more significant estimates and assumptions inherent in this approach include: the amount and timing of the projected net cash flows, which includes the expected impact of competitive, legal and/or regulatory forces on the projections and the impact of technological risk associated with IPR&D assets, as well as the selection of a long-term growth rate; the discount rate, which seeks to reflect the various risks inherent in the projected cash flows; and the tax rate, which seeks to incorporate the geographic diversity of the projected cash flows.

While all intangible assets other than goodwill can face events and circumstances that can lead to impairment, in general, intangible assets other than goodwill that are most at risk of impairment include IPR&D assets (approximately $443 million as of December 31, 2013) and newly acquired or recently impaired indefinite-lived brand assets (approximately $1.5 billion as of December 31, 2013). IPR&D assets are high-risk assets, as research and development is an inherently risky activity. Newly acquired and recently impaired indefinite-lived assets are more vulnerable to impairment as the assets are recorded at fair value and are then subsequently measured at the lower of fair value or carrying value at the end of each reporting period. As such, immediately after acquisition or impairment, even small declines in the outlook for these assets can negatively impact our ability to recover the carrying value and can result in an impairment charge.

• One of our indefinite-lived biopharmaceutical brands, Xanax/Xanax XR, was written down to its fair value of $1.2 billion at the end of the third quarter of 2013. This asset continues to be at risk for future impairment. Any negative change in the undiscounted cash flows, discount rate and/or tax rate could result in an impairment charge. Xanax/Xanax XR, which was launched in the mid-1980s and acquired in 2003, must continue to remain competitive against its generic challengers or the associated asset may become impaired again. We re- considered and confirmed the classification of this asset as indefinite-lived at the time of the impairment. We will continue to closely monitor this asset.

Goodwill

As a result of our goodwill impairment review work, we concluded that none of our goodwill is impaired as of December 31, 2013, and we do not believe the risk of impairment is significant at this time.

For a description of our accounting policy, see Notes to Consolidated Financial Statements—Note 1K. Basis of Presentation and Significant Accounting Policies: Amortization of Intangible Assets, Depreciation and Certain Long-Lived Assets.

When we are required to determine the fair value of a reporting unit, as appropriate for the individual reporting unit, we may use the market approach, the income approach or a weighted-average combination of both approaches.

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The market approach is a historical approach to estimating fair value and relies primarily on external information. Within the market approach are two methods that we