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 may use:

Guideline public company method—this method employs market multiples derived from market prices of stocks of companies that are engaged in the same or similar lines of business and that are actively traded on a free and open market and the application of the identified multiples to the corresponding measure of our reporting unit’s financial performance.

Guideline transaction method—this method relies on pricing multiples derived from transactions of significant interests in companies engaged in the same or similar lines of business and the application of the identified multiples to the corresponding measure of our reporting unit’s financial performance.

The market approach is only appropriate when the available external information is robust and deemed to be a reliable proxy for the specific reporting unit being valued; however, these assessments may prove to be incomplete or inaccurate. Some of the more significant estimates and assumptions inherent in this approach include: the selection of appropriate guideline companies and transactions and the determination of applicable premiums and discounts based on any differences in ownership percentages, ownership rights, business ownership forms or marketability between the reporting unit and the guideline companies and transactions.

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.

Specifically:

• When we estimate the fair value of our five biopharmaceutical reporting units as in effect prior to our January 1, 2014 reorganization we rely solely on the income approach. We use the income approach exclusively as many of our products are sold in multiple reporting units and as one reporting unit is geographic-based while the others are product and/or customer-based. Further, the projected cash flows from a single product may reside in up to three reporting units at different points in future years and the discounted cash flow method would reflect the movement of products among reporting units. As such, the use of the comparable guideline company method is not practical or reliable. For