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 $387 million as of December 31, 2014) and newly acquired or recently impaired indefinite-lived brand assets (approximately $300 million as of December 31, 2014). 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.

Goodwill

As a result of our goodwill impairment review work, we concluded that none of our goodwill was impaired as of December 31, 2014, and we do not believe the risk of impairment is significant at this time.

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

• The income approach is a forward-looking approach to estimating fair value and relies primarily on internal forecasts. Within the income approach, the method that we use is the discounted cash flow method. We start with a forecast of all the expected net cash flows associated with the reporting unit, which includes the application of a terminal value, and then we apply a reporting unit-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 technological risk and competitive, legal and/ or regulatory forces on the projections, 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.

• The market approach is a historical approach to estimating fair value and relies primarily on external