United states securities and exchange commission

Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)
F- 45
Omnibus Plan
In June 2017 our shareholders approved the 2017 Omnibus Equity Plan for share-based awards to our 
employees. Awards granted from the 2017 Omnibus Equity Plan may include stock options, shares of restricted 
stock, RSUs, performance shares, stock appreciation rights and other awards in such amounts and with such terms 
and conditions as may be determined by a committee of our Board of Directors, subject to the provisions of the plan. 
Shares of common stock available for grant under the 2017 Omnibus Equity Plan consist of 8.0 million shares 
reserved for this purpose, plus shares of common stock that remained available for grant under our 2008 Omnibus 
Equity Plan as of June 7, 2017 or that could again become available for grant if outstanding awards under the 2008 
Omnibus Equity Plan as of June 7, 2017 are cancelled, surrendered or terminated in whole or in part. The 2017 
Omnibus Equity Plan provides that awards other than stock options and stock appreciation rights will be counted 
against the total number of shares available under the plan in a 1.5-to-1 ratio.
We have not made any awards pursuant to the 2008 Omnibus Equity Plan since our shareholders approved the 
2017 Omnibus Equity Plan, and do not intend to make any awards pursuant to the 2008 Omnibus Equity Plan in the 
future, except that unused shares under the 2008 Omnibus Equity Plan have been carried over for use under the 
2017 Omnibus Equity Plan.
Stock Options
We currently do not grant stock options to our employees or directors. Outstanding stock options previously 
granted to our employees and directors generally have a ten-year term and vest over a period of between one and 
four years, provided the individual continues to serve at Biogen through the vesting dates. Options granted under all 
plans are exercisable at a price per share not less than the fair market value of the underlying common stock on the 
date of grant. The estimated fair value of options, including the effect of estimated forfeitures, is recognized over the 
options’ vesting periods. The fair value of the stock options granted in 2010 was estimated as of the date of grant 
using a Black-Scholes option valuation model. There were no grants of stock options made in 2017, 2016 and 
2015. As of December 31, 2017, all outstanding options were exercisable.
The expected life of options granted is derived using assumed exercise rates based on historical exercise 
patterns and represents the period of time that options granted are expected to be outstanding. Expected stock 
price volatility is based upon implied volatility for our exchange-traded options and other factors, including historical 
volatility. After assessing all available information on either historical volatility, implied volatility or both, we have 
concluded that a combination of both historical and implied volatility provides the best estimate of expected volatility. 
The risk-free interest rate used is determined by the market yield curve based upon risk-free interest rates 
established by the Federal Reserve, or non-coupon bonds that have maturities equal to the expected term. The 
dividend yield of zero is based upon the fact that we have not historically granted cash dividends, and do not expect 
to issue dividends in the foreseeable future. Stock options granted prior to January 1, 2006 were valued based on 
the grant date fair value of those awards, using the Black-Scholes option pricing model, as previously calculated for 
pro-forma disclosures.
The following table summarizes our stock option activity:
Shares
Weighted
Average
Exercise
Price
Outstanding at December 31, 2016
66,000 $
54.06
Hemophilia spin-off adjustment
— $
—
Granted
— $
—
Exercised
(14,000) $
50.89
Cancelled
(10,000) $
55.11
Outstanding at December 31, 2017
42,000 $
53.83
The total intrinsic values of options exercised in 2017, 2016 and 2015 totaled $3.4 million, $10.4 million and 
$38.0 million, respectively. The aggregate intrinsic values of options outstanding as of December 31, 2017 totaled 
$11.1 million. The weighted average remaining contractual term for options outstanding as of December 31, 2017 
was 1.3 years. 

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Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)
F- 46
The following table summarizes the amount of tax benefit realized for stock options and cash received from the 
exercise of stock options:
 
For the Years Ended December 31,
(In millions)
2017
2016
2015
Tax benefit realized for stock options
$
3.4
$
4.0 $
11.9
Cash received from the exercise of stock options
$
0.7
$
2.2 $
6.3
Market Stock Units (MSUs)
MSUs awarded to employees prior to 2014 vested in four equal annual increments beginning on the first 
anniversary of the grant date. Participants may ultimately earn between 0% and 150% of the target number of units 
granted based on actual stock performance. 
MSUs awarded to employees in 2014 and thereafter vest in three equal annual increments beginning on the 
first anniversary of the grant date, and participants may ultimately earn between 0% and 200% of the target number 
of units granted based on actual stock performance. 
The vesting of these awards is subject to the respective employee’s continued employment. The number of 
MSUs granted represents the target number of units that are eligible to be earned based on the attainment of 
certain market-based criteria involving our stock price. The number of MSUs earned is calculated at each annual 
anniversary from the date of grant over the respective vesting periods, resulting in multiple performance periods. 
Accordingly, additional MSUs may be issued or currently outstanding MSUs may be cancelled upon final 
determination of the number of awards earned. Compensation expense, including the effect of forfeitures, is 
recognized over the applicable service period.
The following table summarizes our MSU activity:
Shares
Weighted
Average
Grant Date
Fair Value
Unvested at December 31, 2016
230,000 $
355.60
Hemophilia spin-off adjustment
4,000 $
—
Granted (a)
94,000 $
382.59
Vested
(112,000) $
311.17
Forfeited
(45,000) $
372.35
Unvested at December 31, 2017
171,000 $
370.83
(a) 
MSUs granted in 2017 include approximately 9,000 MSUs issued in 2017 based upon the attainment of performance 
criteria set for 2013, in relation to awards granted in that year. MSUs granted during 2017 also include awards granted in 
conjunction with our annual awards made in February 2017 and MSUs granted in conjunction with the hiring of employees. 
These grants reflect the target number of shares eligible to be earned at the time of grant. MSUs granted in 2017 reflect an 
adjustment based upon the final performance multiplier in relation to shares granted in 2016, 2015 and 2014.
We value grants of MSUs using a lattice model with a Monte Carlo simulation. This valuation methodology 
utilizes several key assumptions, including the 60 calendar day average closing stock price on grant date for MSUs 
awarded prior to 2014, the 30 calendar day average closing stock price on the date of grant for MSUs awarded in 
2014 and thereafter, expected volatility of our stock price, risk-free rates of return and expected dividend yield.
 The assumptions used in our valuation are summarized as follows:
 
For the Years Ended December 31,
 
2017
2016
2015
Expected dividend yield
—%
—%
—%
Range of expected stock price volatility
33.0% - 35.6%
38.2% - 40.7%
31.0% - 33.2%
Range of risk-free interest rates
0.9% - 1.6%
0.6% - 0.9%
0.2% - 1.0%
30 calendar day average stock price on grant date
$263.18 - $267.88
$260.67 - $304.86 $277.35 - $426.27
Weighted-average per share grant date fair value
$382.59
$328.03
$493.43

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