with APB No.25.
Instead, companies will be required to account for such transactions using a fair-value method and recognize the related expense associated with share-based payments in the statement of operations.
SFAS 123R is effective for us as of January 1, 2006.
We have historically accounted for share-based payments to employees under APB No.25’s intrinsic value method.
As such, we generally have not recognized compensation expense for options granted to employees.
We will adopt the provisions of SFAS 123R under the modified prospective method, in which compensation cost for all share-based payments granted or modified after the effective date is recognized based upon the requirements of SFAS 123R, and compensation cost for all awards granted to employees prior to the effective date that are unvested as of the effective date of SFAS 123R is recognized based on SFAS 123.
Tax benefits will be recognized related to the cost for share-based payments to the extent the equity instrument would ordinarily result in a future tax deduction under existing law.
Tax expense will be recognized to write off excess deferred tax assets when the tax deduction upon settlement of a vested option is less than the expense recorded in the statement of operations (to the extent not offset by prior tax credits for settlements where the tax deduction was greater than the fair value cost).
We estimate that we will recognize equity-based compensation expense of approximately $35 million to $38 million for the year ending December 31, 2006.
This amount is subject to revisions as we finalize certain assumptions related to 2006, including the size and nature of awards and forfeiture rates.
SFAS 123R also requires the benefits of tax deductions in excess of recognized compensation cost be reported as a financing cash flow rather than as operating cash flow as was previously required.
We cannot estimate what the future tax benefits will be as the amounts depend on, among other factors, future employee stock option exercises.
Due to the our tax loss position, there was no operating cash inflow realized for December 31, 2005 and 2004 for such excess tax deductions.
In March 2005, the SEC issued Staff Accounting Bulletin (SAB) No.107 regarding the Staff’s interpretation of SFAS 123R.
This interpretation provides the Staff’s views regarding interactions between SFAS 123R and certain SEC rules and regulations and provides interpretations of the valuation of share-based payments for public companies.
The interpretive guidance is intended to assist companies in applying the provisions of SFAS 123R and investors and users of the financial statements in analyzing the information provided.
We will follow the guidance prescribed in SAB No.107 in connection with our adoption of SFAS 123R.
Information Presented Pursuant to the Indentures of our 7.50% Notes, 7.125% Notes and ATI 7.25% Notes The following table sets forth information that is presented solely to address certain tower cash flow reporting requirements contained in the indentures for our 7.50% Notes, 7.125% Notes and ATI 7.25% Notes.
The information contained in note 19 to our consolidated financial statements is also presented to address certain reporting requirements contained in the indenture for our ATI 7.25% Notes.
The following table presents Tower Cash Flow, Adjusted Consolidated Cash Flow and Non-Tower Cash Flow for the Company and its restricted subsidiaries, as defined in the indentures for the applicable notes (in thousands):
## Table 0 ##
BIOGEN INC.  AND SUBSIDIARIES NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued) F- 46 During 2013, we recorded a deferred charge of $203.7 million in connection with an intercompany transfer of the intellectual property for ZINBRYTA.
The net book value of this deferred charge as of December 31, 2015 and 2014 was $166.3 million and $179.9 million, respectively.
The deferred charge will be amortized to income tax expense over the economic life of the ZINBRYTA program.
Our regulatory submissions in Europe and the U. S.  have been accepted for review by the relevant authorities.
If the ZINBRYTA applications are not approved, we may have to accelerate the amortization of this deferred charge and record an expense equal to its remaining net book value.
Tax Rate A reconciliation between the U. S.  federal statutory tax rate and our effective tax rate is summarized as follows:
## Table 1 ##
Our effective tax rate for 2015 compared to 2014 benefited from lower anticipated taxes on foreign earnings and reflects a $27.0 million benefit from the 2015 remeasurement of one of our uncertain tax positions, described below under "Accounting for Uncertainty in Income Taxes".
Our effective tax rate for 2014 compared to 2013 increased primarily as a result of the absence of a benefit related to the 2013 change in our uncertain tax position related to our U. S.  federal manufacturing deduction and our unconsolidated joint business described below under "Accounting for Uncertainty in Income Taxes", lower current year expenses eligible for the orphan drug credit and a lower relative manufacturing deduction due to unqualified products, partially offset by a higher percentage of our 2014 income being earned outside the U. S.  As of December 31, 2015, we had net operating losses and general business credit carry forwards for federal income tax purposes of approximately $25.3 million and $127.6 million, respectively, which begin to expire in 2020.
Additionally, for state income tax purposes, we had net operating loss carry forwards of approximately $91.7 million, which begin to expire in 2016.
For state income tax purposes, we also had research and investment credit carry forwards of approximately $125.5 million, which begin to expire in 2016.
For foreign income tax purposes, we had $53.4 million of net operating loss carryforwards, which begin to expire in 2021.
In assessing the realizability of our deferred tax assets, we have considered whether it is more likely than not that some portion or all of the deferred tax assets will not be realized.
The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible.
In making this determination, under the applicable financial reporting standards, we are allowed to consider the scheduled reversal of deferred tax liabilities, projected future taxable income, and tax planning strategies.
Our estimates of future taxable income take into consideration, among other items, our estimates of future income tax deductions related to the exercise of stock options.
Based upon the level of historical taxable income and income tax liability and projections for future taxable income over the periods in which the deferred tax assets are utilizable, we believe it is more likely than not that we will realize the benefits of the deferred tax assets of our wholly owned subsidiaries.
In the event that actual results differ from our estimates or we adjust our estimates in future periods, we may need to establish a valuation allowance, which could materially impact our financial position and results of operations.
As of December 31, 2015, undistributed foreign earnings of non-U.
S.  subsidiaries included in consolidated retained earnings and other basis differences aggregated approximately $6.0 billion.
We intend to reinvest these earnings indefinitely in operations outside the U. S.  The residual U. S.  tax liability, if cumulative amounts were repatriated, would be between $1.5 billion to $2.0 billion as of December 31, 2015.
BIOGEN INC.  AND SUBSIDIARIES NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued) F- 64 Securities Litigation We and certain current and former officers are defendants in In re Biogen Inc.  Securities Litigation, filed by a shareholder on August 18, 2015 in the U. S.  District Court for the District of Massachusetts.
The amended complaint alleges violations of federal securities laws under 15 U. S. C.  §78j(b) and §78t(a) and 17 C. F. R.  §240.10b-5.
The lead plaintiff seeks a declaration of the action as a class action, certification as a representative of the class and its counsel as class counsel, and an award of damages, interest, and attorneys' fees.
An estimate of the possible loss or range of loss cannot be made at this time.
Product Liability and Other Legal Proceedings We are also involved in product liability claims and other legal proceedings generally incidental to our normal business activities.
While the outcome of any of these proceedings cannot be accurately predicted, we do not believe the ultimate resolution of any of these existing matters would have a material adverse effect on our business or financial condition.21.
Commitments and Contingencies Leases We rent laboratory and office space and certain equipment under non-cancelable operating leases.
These lease agreements contain various clauses for renewal at our option and, in certain cases, escalation clauses typically linked to rates of inflation.
Rental expense under these leases, net of amounts recognized in relation to exiting our Weston, Massachusetts facility, which terminate at various dates through 2028, amounted to $68.6 million and $62.4 million in 2015 and 2014, respectively.
Rent expense was $56.1 million in 2013.
In addition to rent, the leases may require us to pay additional amounts for taxes, insurance, maintenance and other operating expenses.
As of December 31, 2015, minimum rental commitments under non-cancelable leases, net of income from subleases, for each of the next five years and total thereafter were as follows:
## Table 2 ##
(1) As a result of our decision to relocate our corporate headquarters to Cambridge, Massachusetts, we vacated part of our Weston, Massachusetts facility in the fourth quarter of 2013.
We incurred a charge of $27.2 million in connection with this move.
This charge represented our remaining lease obligation for the vacated portion of our Weston, Massachusetts facility, net of sublease income expected to be received.
The term of our sublease to the vacated portion of our Weston, Massachusetts facility started in January 2014 and will continue through the remaining term of our lease agreement.
Under certain of our lease agreements, we are contractually obligated to return leased space to its original condition upon termination of the lease agreement.
At the inception of a lease with such conditions, we record an asset retirement obligation liability and a corresponding capital asset in an amount equal to the estimated fair value of the obligation.
In subsequent periods, for each such lease, we record interest expense to accrete the asset retirement obligation liability to full value and depreciate each capitalized asset retirement obligation asset, both over the term of the associated lease agreement.
Our asset retirement obligations were not significant as of December 31, 2015 or 2014.
BIOGEN INC.  AND SUBSIDIARIES NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued) F- 68 24.
Segment Information We operate as one operating segment, which is discovering, developing, manufacturing and delivering therapies to patients for the treatment of neurodegenerative diseases, hematologic conditions and autoimmune disorders, and, therefore, our chief operating decision-maker manages the operations of our company as a single operating segment.
Enterprise-wide disclosures about product revenues, other revenues and long-lived assets by geographic area and information relating to major customers are presented below.
Revenues are primarily attributed to individual countries based on location of the customer or licensee.
Revenue by product is summarized as follows:
## Table 3 ##
Geographic Information The following tables contain certain financial information by geographic area:
## Table 4 ##
(1) Represents amounts related to Europe less those attributable to Germany

<table><tr><td>Tower Cash Flow, for the three months ended December 31, 2005</td><td>$139,590</td></tr><tr><td>Consolidated Cash Flow, for the twelve months ended December 31, 2005</td><td>$498,266</td></tr><tr><td>Less: Tower Cash Flow, for the twelve months ended December 31, 2005</td><td>-524,804</td></tr><tr><td>Plus: four times Tower Cash Flow, for the three months ended December 31, 2005</td><td>558,360</td></tr><tr><td>Adjusted Consolidated Cash Flow, for the twelve months ended December 31, 2005</td><td>$531,822</td></tr><tr><td>Non-Tower Cash Flow, for the twelve months ended December 31, 2005</td><td>$-30,584</td></tr></table>
<table><tr><td></td><td colspan="3">For the Years Ended December 31,</td></tr><tr><td></td><td>2015</td><td>2014</td><td>2013</td></tr><tr><td>Statutory rate</td><td>35.0%</td><td>35.0%</td><td>35.0%</td></tr><tr><td>State taxes</td><td>0.5</td><td>1.2</td><td>3.1</td></tr><tr><td>Taxes on foreign earnings</td><td>-10.0</td><td>-9.5</td><td>-6.7</td></tr><tr><td>Credits and net operating loss utilization</td><td>-1.3</td><td>-1.1</td><td>-2.6</td></tr><tr><td>Purchased intangible assets</td><td>1.0</td><td>1.2</td><td>1.5</td></tr><tr><td>Manufacturing deduction</td><td>-1.8</td><td>-1.8</td><td>-6.6</td></tr><tr><td>Other permanent items</td><td>0.7</td><td>0.5</td><td>0.8</td></tr><tr><td>Contingent consideration and other</td><td>0.3</td><td>-0.4</td><td>-0.3</td></tr><tr><td>Effective tax rate</td><td>24.4%</td><td>25.1%</td><td>24.2%</td></tr></table>
<table><tr><td>(In millions)</td><td>2016</td><td>2017</td><td>2018</td><td>2019</td><td>2020</td><td>Thereafter</td><td>Total</td></tr><tr><td>Minimum lease payments -1</td><td>$75.9</td><td>$75.7</td><td>$67.9</td><td>$66.7</td><td>$63.2</td><td>$382.7</td><td>$732.1</td></tr><tr><td>Less: income from subleases</td><td>-6.0</td><td>-6.0</td><td>-6.3</td><td>-6.3</td><td>-6.3</td><td>-28.9</td><td>-59.8</td></tr><tr><td>Net minimum lease payments</td><td>$69.9</td><td>$69.7</td><td>$61.6</td><td>$60.4</td><td>$56.9</td><td>$353.8</td><td>$672.3</td></tr></table>
<table><tr><td></td><td colspan="9">For the Years Ended December 31,</td></tr><tr><td></td><td colspan="3">2015</td><td colspan="3">2014</td><td colspan="3">2013</td></tr><tr><td>(In millions)</td><td>UnitedStates</td><td>Rest ofWorld</td><td>Total</td><td>UnitedStates</td><td>Rest ofWorld</td><td>Total</td><td>UnitedStates</td><td>Rest ofWorld</td><td>Total</td></tr><tr><td>Multiple Sclerosis (MS):</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>TECFIDERA</td><td>$2,908.2</td><td>$730.2</td><td>$3,638.4</td><td>$2,426.6</td><td>$482.6</td><td>$2,909.2</td><td>$864.4</td><td>$11.7</td><td>$876.1</td></tr><tr><td>AVONEX</td><td>1,790.2</td><td>840.0</td><td>2,630.2</td><td>1,956.7</td><td>1,056.4</td><td>3,013.1</td><td>1,902.4</td><td>1,103.1</td><td>3,005.5</td></tr><tr><td>PLEGRIDY</td><td>227.1</td><td>111.4</td><td>338.5</td><td>27.8</td><td>16.7</td><td>44.5</td><td>—</td><td>—</td><td>—</td></tr><tr><td>TYSABRI</td><td>1,103.1</td><td>783.0</td><td>1,886.1</td><td>1,025.1</td><td>934.4</td><td>1,959.5</td><td>814.2</td><td>712.3</td><td>1,526.5</td></tr><tr><td>FAMPYRA</td><td>—</td><td>89.7</td><td>89.7</td><td>—</td><td>80.2</td><td>80.2</td><td>—</td><td>74.0</td><td>74.0</td></tr><tr><td>Hemophilia:</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>ELOCTATE</td><td>308.3</td><td>11.4</td><td>319.7</td><td>58.4</td><td>—</td><td>58.4</td><td>—</td><td>—</td><td>—</td></tr><tr><td>ALPROLIX</td><td>208.9</td><td>25.6</td><td>234.5</td><td>72.1</td><td>3.9</td><td>76.0</td><td>—</td><td>—</td><td>—</td></tr><tr><td>Other product revenues:</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>FUMADERM</td><td>—</td><td>51.4</td><td>51.4</td><td>—</td><td>62.5</td><td>62.5</td><td>—</td><td>60.2</td><td>60.2</td></tr><tr><td>Total product revenues</td><td>$6,545.8</td><td>$2,642.7</td><td>$9,188.5</td><td>$5,566.7</td><td>$2,636.7</td><td>$8,203.4</td><td>$3,581.0</td><td>$1,961.3</td><td>$5,542.3</td></tr></table>
<table><tr><td>December 31, 2015 (In millions)</td><td>U.S.</td><td>Europe<sup>-1</sup></td><td>Germany</td><td>Asia</td><td>Other</td><td>Total</td></tr><tr><td>Product revenues from external customers</td><td>$6,545.8</td><td>$1,497.6</td><td>$668.1</td><td>$143.7</td><td>$333.3</td><td>$9,188.5</td></tr><tr><td>Unconsolidated joint business revenues</td><td>$1,269.8</td><td>$3.5</td><td>$—</td><td>$—</td><td>$65.9</td><td>$1,339.2</td></tr><tr><td>Other revenues from external customers</td><td>$142.0</td><td>$29.6</td><td>$1.6</td><td>$62.9</td><td>$—</td><td>$236.1</td></tr><tr><td>Long-lived assets</td><td>$1,296.5</td><td>$879.4</td><td>$2.3</td><td>$7.7</td><td>$1.7</td><td>$2,187.6</td></tr><tr><td>December 31, 2014 (In millions)</td><td>U.S.</td><td>Europe<sup>-1</sup></td><td>Germany</td><td>Asia</td><td>Other</td><td>Total</td></tr><tr><td>Product revenues from external customers</td><td>$5,566.7</td><td>$1,383.9</td><td>$811.8</td><td>$112.8</td><td>$328.2</td><td>$8,203.4</td></tr><tr><td>Unconsolidated joint business revenues</td><td>$1,117.1</td><td>$7.7</td><td>$—</td><td>$—</td><td>$70.6</td><td>$1,195.4</td></tr><tr><td>Other revenues from external customers</td><td>$212.6</td><td>$31.6</td><td>$1.8</td><td>$58.5</td><td>$—</td><td>$304.5</td></tr><tr><td>Long-lived assets</td><td>$1,055.5</td><td>$701.9</td><td>$2.5</td><td>$2.6</td><td>$3.2</td><td>$1,765.7</td></tr><tr><td>December 31, 2013 (In millions)</td><td>U.S.</td><td>Europe<sup>-1</sup></td><td>Germany</td><td>Asia</td><td>Other</td><td>Total</td></tr><tr><td>Product revenues from external customers</td><td>$3,581.0</td><td>$1,170.2</td><td>$417.7</td><td>$93.2</td><td>$280.2</td><td>$5,542.3</td></tr><tr><td>Unconsolidated joint business revenues</td><td>$1,087.3</td><td>$1.6</td><td>$—</td><td>$3.2</td><td>$33.9</td><td>$1,126.0</td></tr><tr><td>Other revenues from external customers</td><td>$193.5</td><td>$26.1</td><td>$1.2</td><td>$43.1</td><td>$—</td><td>$263.9</td></tr><tr><td>Long-lived assets</td><td>$984.4</td><td>$758.3</td><td>$2.5</td><td>$2.1</td><td>$3.3</td><td>$1,750.7</td></tr></table>

Question: Which year is Product revenues from external customers the most?
Answer: December 31, 2015