BIOGEN INC

Ticker: BIIB CUSIP: 09062X103 Class: COM

VIKING GLOBAL INVESTORS LP's Holding History (CIK: 0001103804)

Note: Option positions (PUT/CALL) are excluded.

Q1 2017

Shares 688,765 Value ($000) $188,322 Avg Close $282.75 Range $260.50 - $301.42

Q4 2016

Shares 1,918,812 Value ($000) $544,137 Avg Close $296.43 Range $268.00 - $329.83

Q3 2016

Shares 2,186,336 Value ($000) $684,389 Avg Close $296.18 Range $240.07 - $333.65

Q2 2016

Shares 3,210,507 Value ($000) $776,365 Avg Close $263.54 Range $223.02 - $292.69

Q1 2016

Shares 230,947 Value ($000) $60,120 Avg Close $264.15 Range $242.07 - $301.02

Q4 2015

Shares 368,864 Value ($000) $113,001 Avg Close $287.35 Range $254.00 - $311.65

Q2 2015

Shares 513,444 Value ($000) $207,401 Avg Close $401.33 Range $368.88 - $432.88

Q1 2014

Shares 388,900 Value ($000) $118,953 Avg Close $317.43 Range $270.62 - $358.89

Q3 2013

Shares 290,345 Value ($000) $69,903 Avg Close $223.81 Range $203.55 - $248.95

Q2 2013

Shares 966,288 Value ($000) $207,945 Avg Close $213.68 Range $191.80 - $242.64

Period	Shares	Value ($000)	Average Close	Price Range
Q1 2017	688,765	$188,322	$282.75	$260.50 - $301.42
Q4 2016	1,918,812	$544,137	$296.43	$268.00 - $329.83
Q3 2016	2,186,336	$684,389	$296.18	$240.07 - $333.65
Q2 2016	3,210,507	$776,365	$263.54	$223.02 - $292.69
Q1 2016	230,947	$60,120	$264.15	$242.07 - $301.02
Q4 2015	368,864	$113,001	$287.35	$254.00 - $311.65
Q2 2015	513,444	$207,401	$401.33	$368.88 - $432.88
Q1 2014	388,900	$118,953	$317.43	$270.62 - $358.89
Q3 2013	290,345	$69,903	$223.81	$203.55 - $248.95
Q2 2013	966,288	$207,945	$213.68	$191.80 - $242.64