Biogen Inc.
US ˙ NasdaqGS ˙ US09062X1037

SecurityBIIB / Biogen Inc.
InstitutionCitigroup Inc
Latest Disclosed Ownership500,507 shares
Latest Disclosed Value $ 91,757,948
Citigroup Inc ownership in BIIB / Biogen Inc.

On May 11, 2026 - Citigroup Inc filed a 13F-HR form disclosing ownership of 500,507 shares of Biogen Inc. (US:BIIB) valued at $91,757,948 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 13, 2026 disclosing 573,844 shares of Biogen Inc.. This represents a change in shares of -12.78% during the quarter. The current value of the position is $98,079,352 USD.

Citigroup Inc has a history of taking positions in derivatives of the underlying security (BIIB) in the form of stock options. The firm currently holds call options representing 21,200 of underlying shares valued at $3,886,596 USD and put options representing 0 of underlying shares valued at $0 USD .

Note: prior versions of this page mistakenly stated that the share values represented the number of options, not the number of underlying shares. For more information on the data backing these reports, please see the SEC document Frequently Asked Questions About Form 13F.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Institutional Put/Call Ratios
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In addition to reporting standard equity and debt issues, institutions with more than 100MM assets under management must also disclose their put and call option holdings. Since put options generally indicate negative sentiment, and call options indicate positive sentiment, we can get a sense of the overall institutional sentiment by plotting the ratio of puts to calls. The chart to the right plots the historical put/call ratio for this instrument.

Using Put/Call Ratio as an indicator of investor sentiment overcomes one of the key deficiencies of using total institutional ownership, which is that a significant amount of assets under management are invested passively to track indices. Passively-managed funds do not typically buy options, so the put/call ratio indicator more closely tracks the sentiment of actively-managed funds.

BIIB / Biogen Inc. Historical Put/Call Ratio
Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date
Effective
Date
Form Security Class ID Avg Price
Paid (Est)
Reported
Shares
ΔShares ΔShares
(%)
Reported
Value
(x1000)
ΔValue
(%)
Alloc
(%)
ΔAlloc ΔAlloc (%) Cost Basis
(x1000)
Unrealized
Gain/Loss
(x1000)
2026-05-11 2026-03-31 13F BIOGEN COM 09062X103 500,507 -73,337 -12.78 91,758 -9.14 0.0391
2026-02-13 2025-12-31 13F BIOGEN COM 09062X103 573,844 371,545 183.66 100,991 256.38 0.0446
2025-11-10 2025-09-30 13F BIOGEN COM 09062X103 202,299 -20,941 -9.38 28,338 1.08 0.0126
2025-08-11 2025-06-30 13F BIOGEN COM 09062X103 223,240 -79,375 -26.23 28,037 -32.29 0.0138
2025-05-12 2025-03-31 13F BIOGEN COM 09062X103 302,615 38,276 14.48 41,410 2.44 0.0212
2025-02-12 2024-12-31 13F BIOGEN COM 09062X103 264,339 26,191 11.00 40,423 -12.43 0.0240
2024-11-12 2024-09-30 13F BIOGEN COM 09062X103 238,148 14,801 6.63 46,163 -10.84 0.0267
2024-08-12 2024-06-30 13F BIOGEN COM 09062X103 223,347 4,630 2.12 51,776 9.79 0.0332
2024-05-10 2024-03-31 13F BIOGEN COM 09062X103 218,717 -1,936 -0.88 47,162 -17.40 0.0310
2024-02-09 2023-12-31 13F BIOGEN COM 09062X103 220,653 -1,105 -0.50 57,098 0.18 0.0402
2023-12-06 2023-09-30 13F/A-1 BIOGEN COM 09062X103 221,758 -13,144 -5.60 56,994 -14.82 0.0426
2023-11-09 2023-09-30 13F BIOGEN COM 09062X103 221,758 -13,144 56,994 0.0170
2023-08-10 2023-06-30 13F BIOGEN COM 09062X103 234,902 4,936 2.15 66,912 4.65 0.0439
2023-05-11 2023-03-31 13F BIOGEN COM 09062X103 229,966 33,140 16.84 63,937 17.30 0.0448
2023-02-09 2022-12-31 13F BIOGEN COM 09062X103 196,826 -58,384 -22.88 54,505 -20.01 0.0434
2022-11-10 2022-09-30 13F BIOGEN COM 09062X103 255,210 68,887 36.97 68,141 79.33 0.0488
2022-08-10 2022-06-30 13F BIOGEN COM 09062X103 186,323 -19,455 -9.45 37,997 -12.32 0.0283
2022-05-12 2022-03-31 13F BIOGEN COM 09062X103 205,778 -176,956 -46.23 43,336 -52.81 0.0263
2022-02-10 2021-12-31 13F BIOGEN COM 09062X103 382,734 112,061 41.40 91,826 19.88 0.0492
2021-11-10 2021-09-30 13F BIOGEN COM 09062X103 270,673 -4,862 -1.76 76,597 -19.72 0.0452
2021-08-10 2021-06-30 13F BIOGEN COM 09062X103 275,535 22,747 9.00 95,409 34.91 0.0574
2021-05-13 2021-03-31 13F BIOGEN COM 09062X103 252,788 -40,462 -13.80 70,719 -1.51 0.0457
2021-02-11 2020-12-31 13F BIOGEN COM 09062X103 293,250 96,447 49.01 71,804 28.62 0.0424
2020-11-12 2020-09-30 13F BIOGEN COM 09062X103 196,803 -21,834 -9.99 55,828 -4.56 0.0364
2020-08-12 2020-06-30 13F BIOGEN COM 09062X103 218,637 9,744 4.66 58,495 -11.49 0.0457
2020-05-12 2020-03-31 13F BIOGEN COM 09062X103 208,893 -95,288 -31.33 66,090 -26.78 0.0597
2020-02-12 2019-12-31 13F BIOGEN COM 09062X103 304,181 39,825 15.06 90,259 46.65 0.0653
2019-11-08 2019-09-30 13F BIOGEN COM 09062X103 264,356 -20,717 -7.27 61,546 -7.69 0.0488
2019-08-12 2019-06-30 13F BIOGEN COM 09062X103 285,073 101,349 55.16 66,671 53.51 0.0539
2019-05-13 2019-03-31 13F BIOGEN COM 09062X103 183,724 -57,829 -23.94 43,430 -40.25 0.0419
2019-02-12 2018-12-31 13F BIOGEN COM 09062X103 241,553 40,590 20.20 72,689 2.38 0.0736
2018-11-13 2018-09-30 13F BIOGEN COM 09062X103 200,963 23,468 13.22 71,002 37.83 0.0633
2018-08-10 2018-06-30 13F BIOGEN COM 09062X103 177,495 -104,295 -37.01 51,516 -33.23 0.0473
2018-05-11 2018-03-31 13F BIOGEN COM 09062X103 281,790 46,256 19.64 77,160 2.83 0.0636
2018-02-12 2017-12-31 13F BIOGEN COM 09062X103 235,534 -47,325 -16.73 75,035 -15.28 0.0601
2017-11-13 2017-09-30 13F BIOGEN COM 09062X103 282,859 103,751 57.93 88,569 82.23 0.0725
2017-08-11 2017-06-30 13F BIOGEN COM 09062X103 179,108 45,172 33.73 48,603 32.72 0.0438
2017-05-12 2017-03-31 13F BIOGEN COM 09062X103 133,936 -97,682 -42.17 36,620 -44.25 0.0326
2017-02-10 2016-12-31 13F BIOGEN COM 09062X103 231,618 154,037 198.55 65,682 170.46 0.0592
2016-11-10 2016-09-30 13F BIOGEN COM 09062X103 77,581 -29,659 -27.66 24,285 -6.35 0.0227
2016-08-12 2016-06-30 13F BIOGEN COM 09062X103 107,240 27,461 34.42 25,933 24.88 0.0265
2016-05-13 2016-03-31 13F BIOGEN COM 09062X103 79,779 -3,126 -3.77 20,767 -18.23 0.0233
2016-02-12 2015-12-31 13F BIOGEN COM 09062X103 82,905 -26,752 -24.40 25,398 -20.63 0.0253
2015-11-13 2015-09-30 13F BIOGEN COM 09062X103 109,657 -31,779 -22.47 31,999 -43.99 0.0299
2015-08-13 2015-06-30 13F BIOGEN COM 09062X103 141,436 -26,927 -15.99 57,132 -19.63 0.0507
2015-05-14 2015-03-31 13F BIOGEN COM 09062X103 168,363 -83,528 -33.16 71,088 -16.86 0.0687
2015-02-17 2014-12-31 13F BIOGEN IDEC COM 09062X103 251,891 127,578 102.63 85,505 107.93 0.0764
2014-11-14 2014-09-30 13F BIOGEN IDEC COM 09062X103 124,313 -39,964 -24.33 41,123 -20.61 0.0360
2014-08-14 2014-06-30 13F BIOGEN IDEC COM 09062X103 164,277 24,839 17.81 51,797 21.45 0.0497
2014-05-15 2014-03-31 13F BIOGEN IDEC COM 09062X103 139,438 -4,007 -2.79 42,650 6.28 0.0436
2014-02-14 2013-12-31 13F BIOGEN IDEC COM 09062X103 143,445 -45,318 -24.01 40,128 -11.70 0.0363
2013-11-14 2013-09-30 13F BIOGEN IDEC COM 09062X103 188,763 -28,063 -12.94 45,446 -2.61 0.0426
2013-08-14 2013-06-30 13F BIOGEN IDEC COM 09062X103 216,826 216,826 46,662 0.0459
Disclosed Call Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share
Price
Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2026-05-11 2026-03-31 13F BIOGEN COM Call 21,200 -73.20 3,887 -72.08 n/a n/a n/a
2026-02-13 2025-12-31 13F BIOGEN COM Call 79,100 0.00 13,921 25.63 n/a n/a n/a
2025-11-10 2025-09-30 13F BIOGEN COM Call 79,100 0.00 11,080 11.54 n/a n/a n/a
2025-08-11 2025-06-30 13F BIOGEN COM Call 79,100 -15.85 9,934 -22.76 n/a n/a n/a
2025-05-12 2025-03-31 13F BIOGEN COM Call 94,000 -42.79 12,863 -48.81 n/a n/a n/a
2025-02-12 2024-12-31 13F BIOGEN COM Call 164,300 5,034.38 25,125 3,952.26 n/a n/a n/a
2024-11-12 2024-09-30 13F BIOGEN COM Call 3,200 -82.42 620 -85.30 n/a n/a n/a
2024-08-12 2024-06-30 13F BIOGEN COM Call 18,200 468.75 4,219 511.45 n/a n/a n/a
2024-05-10 2024-03-31 13F BIOGEN COM Call 3,200 -93.35 690 -94.46 n/a n/a n/a
2024-02-09 2023-12-31 13F BIOGEN COM Call 48,100 -40.02 12,447 -39.62 n/a n/a n/a
2023-12-06 2023-09-30 13F/A BIOGEN COM Call 80,200 99.50 20,612 80.02 n/a n/a n/a
2023-11-09 2023-09-30 13F BIOGEN COM Call 80,200 20,612 n/a n/a n/a
2023-08-10 2023-06-30 13F BIOGEN COM Call 40,200 -38.15 11,451 -36.64 n/a n/a n/a
2023-05-11 2023-03-31 13F BIOGEN COM Call 65,000 18,072 n/a n/a n/a
2023-02-09 2022-12-31 13F BIOGEN COM Call 0 -100.00 0 -100.00 n/a n/a n/a
2022-11-10 2022-09-30 13F BIOGEN COM Call 40,000 60.00 10,680 109.45 n/a n/a n/a
2022-08-10 2022-06-30 13F BIOGEN COM Call 25,000 5,099 n/a n/a n/a
2022-05-12 2022-03-31 13F BIOGEN COM Call 0 -100.00 0 -100.00 n/a n/a n/a
2022-02-10 2021-12-31 13F BIOGEN COM Call 61,000 0.00 14,635 -15.22 n/a n/a n/a
2021-11-10 2021-09-30 13F BIOGEN COM Call 61,000 69.92 17,263 38.87 n/a n/a n/a
2021-08-10 2021-06-30 13F BIOGEN COM Call 35,900 105.14 12,431 153.90 n/a n/a n/a
2021-05-13 2021-03-31 13F BIOGEN COM Call 17,500 -91.35 4,896 -90.12 n/a n/a n/a
2021-02-11 2020-12-31 13F BIOGEN COM Call 202,300 37.25 49,536 18.47 n/a n/a n/a
2020-11-12 2020-09-30 13F BIOGEN COM Call 147,400 28.85 41,814 36.61 n/a n/a n/a
2020-08-12 2020-06-30 13F BIOGEN COM Call 114,400 -25.95 30,608 -37.38 n/a n/a n/a
2020-05-12 2020-03-31 13F BIOGEN COM Call 154,500 -5.04 48,881 1.25 n/a n/a n/a
2020-02-12 2019-12-31 13F BIOGEN COM Call 162,700 35.47 48,278 72.66 n/a n/a n/a
2019-11-08 2019-09-30 13F BIOGEN COM Call 120,100 15.93 27,962 15.41 n/a n/a n/a
2019-08-12 2019-06-30 13F BIOGEN COM Call 103,600 17.33 24,229 16.08 n/a n/a n/a
2019-05-13 2019-03-31 13F BIOGEN COM Call 88,300 -55.72 20,873 -65.21 n/a n/a n/a
2019-02-12 2018-12-31 13F BIOGEN COM Call 199,400 42.02 60,004 20.96 n/a n/a n/a
2018-11-13 2018-09-30 13F BIOGEN COM Call 140,400 -6.09 49,605 14.32 n/a n/a n/a
2018-08-10 2018-06-30 13F BIOGEN COM Call 149,500 8.10 43,392 14.58 n/a n/a n/a
2018-05-11 2018-03-31 13F BIOGEN COM Call 138,300 -21.78 37,869 -32.76 n/a n/a n/a
2018-02-12 2017-12-31 13F BIOGEN COM Call 176,800 9.47 56,323 11.38 n/a n/a n/a
2017-11-13 2017-09-30 13F BIOGEN COM Call 161,500 43.68 50,569 65.79 n/a n/a n/a
2017-08-11 2017-06-30 13F BIOGEN COM Call 112,400 4.46 30,501 3.67 n/a n/a n/a
2017-05-12 2017-03-31 13F BIOGEN COM Call 107,600 -66.27 29,420 -67.48 n/a n/a n/a
2017-02-10 2016-12-31 13F BIOGEN COM Call 319,000 100.50 90,462 81.64 n/a n/a n/a
2016-11-10 2016-09-30 13F BIOGEN COM Call 159,100 43.72 49,803 86.04 n/a n/a n/a
2016-08-12 2016-06-30 13F BIOGEN COM Call 110,700 84.50 26,770 71.39 n/a n/a n/a
2016-05-13 2016-03-31 13F BIOGEN COM Call 60,000 -45.45 15,619 -53.65 n/a n/a n/a
2016-02-12 2015-12-31 13F BIOGEN COM Call 110,000 -46.21 33,698 -43.53 n/a n/a n/a
2015-11-13 2015-09-30 13F BIOGEN COM Call 204,500 34.10 59,675 -3.12 n/a n/a n/a
2015-08-13 2015-06-30 13F BIOGEN COM Call 152,500 111.81 61,600 102.62 n/a n/a n/a
2015-05-14 2015-03-31 13F BIOGEN COM Call 72,000 -15.49 30,401 5.12 n/a n/a n/a
2015-02-17 2014-12-31 13F BIOGEN IDEC COM Call 85,200 9.79 28,921 12.66 n/a n/a n/a
2014-11-14 2014-09-30 13F BIOGEN IDEC COM Call 77,600 -16.65 25,671 -12.55 n/a n/a n/a
2014-08-14 2014-06-30 13F BIOGEN IDEC COM Call 93,100 -34.94 29,355 -32.93 n/a n/a n/a
2014-05-15 2014-03-31 13F BIOGEN IDEC COM Call 143,100 -31.40 43,770 -24.99 n/a n/a n/a
2014-02-14 2013-12-31 13F BIOGEN IDEC COM Call 208,600 -27.04 58,356 -15.22 n/a n/a n/a
2013-11-14 2013-09-30 13F BIOGEN IDEC COM Call 285,900 52.40 68,834 70.50 n/a n/a n/a
2013-08-14 2013-06-30 13F BIOGEN IDEC COM Call 187,600 40,372 n/a n/a n/a
Disclosed Put Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share Price Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2026-05-11 2026-03-31 13F BIOGEN COM Put 0 -100.00 0 -100.00 n/a n/a n/a
2026-02-13 2025-12-31 13F BIOGEN COM Put 14,600 0.00 2,569 25.62 n/a n/a n/a
2025-11-10 2025-09-30 13F BIOGEN COM Put 14,600 0.00 2,045 11.57 n/a n/a n/a
2025-08-11 2025-06-30 13F BIOGEN COM Put 14,600 -50.51 1,834 -54.58 n/a n/a n/a
2025-05-12 2025-03-31 13F BIOGEN COM Put 29,500 10.07 4,037 -1.51 n/a n/a n/a
2025-02-12 2024-12-31 13F BIOGEN COM Put 26,800 458.33 4,098 340.65 n/a n/a n/a
2024-11-12 2024-09-30 13F BIOGEN COM Put 4,800 -75.76 930 -79.74 n/a n/a n/a
2024-08-12 2024-06-30 13F BIOGEN COM Put 19,800 312.50 4,590 343.48 n/a n/a n/a
2024-05-10 2024-03-31 13F BIOGEN COM Put 4,800 -88.49 1,035 -90.41 n/a n/a n/a
2024-02-09 2023-12-31 13F BIOGEN COM Put 41,700 -37.57 10,791 -37.15 n/a n/a n/a
2023-12-06 2023-09-30 13F/A BIOGEN COM Put 66,800 21.90 17,168 9.99 n/a n/a n/a
2023-11-09 2023-09-30 13F BIOGEN COM Put 66,800 17,168 n/a n/a n/a
2023-08-10 2023-06-30 13F BIOGEN COM Put 54,800 66.06 15,610 70.14 n/a n/a n/a
2023-05-11 2023-03-31 13F BIOGEN COM Put 33,000 46.67 9,175 47.26 n/a n/a n/a
2023-02-09 2022-12-31 13F BIOGEN COM Put 22,500 -60.87 6,231 -59.42 n/a n/a n/a
2022-11-10 2022-09-30 13F BIOGEN COM Put 57,500 15,353 n/a n/a n/a
2021-05-13 2021-03-31 13F BIOGEN COM Put 0 -100.00 0 -100.00 n/a n/a n/a
2021-02-11 2020-12-31 13F BIOGEN COM Put 177,800 3.49 43,537 -10.67 n/a n/a n/a
2020-11-12 2020-09-30 13F BIOGEN COM Put 171,800 -7.29 48,736 -1.70 n/a n/a n/a
2020-08-12 2020-06-30 13F BIOGEN COM Put 185,300 -28.43 49,577 -39.47 n/a n/a n/a
2020-05-12 2020-03-31 13F BIOGEN COM Put 258,900 -3.50 81,911 2.89 n/a n/a n/a
2020-02-12 2019-12-31 13F BIOGEN COM Put 268,300 -6.16 79,612 19.60 n/a n/a n/a
2019-11-08 2019-09-30 13F BIOGEN COM Put 285,900 12.38 66,563 11.88 n/a n/a n/a
2019-08-12 2019-06-30 13F BIOGEN COM Put 254,400 44.38 59,496 42.85 n/a n/a n/a
2019-05-13 2019-03-31 13F BIOGEN COM Put 176,200 -42.77 41,650 -55.05 n/a n/a n/a
2019-02-12 2018-12-31 13F BIOGEN COM Put 307,900 1.22 92,653 -13.79 n/a n/a n/a
2018-11-13 2018-09-30 13F BIOGEN COM Put 304,200 5.33 107,477 28.22 n/a n/a n/a
2018-08-10 2018-06-30 13F BIOGEN COM Put 288,800 12.42 83,822 19.16 n/a n/a n/a
2018-05-11 2018-03-31 13F BIOGEN COM Put 256,900 15.00 70,344 -1.16 n/a n/a n/a
2018-02-12 2017-12-31 13F BIOGEN COM Put 223,400 11.37 71,169 13.30 n/a n/a n/a
2017-11-13 2017-09-30 13F BIOGEN COM Put 200,600 41.27 62,812 63.01 n/a n/a n/a
2017-08-11 2017-06-30 13F BIOGEN COM Put 142,000 -26.73 38,533 -27.28 n/a n/a n/a
2017-05-12 2017-03-31 13F BIOGEN COM Put 193,800 -40.46 52,988 -42.59 n/a n/a n/a
2017-02-10 2016-12-31 13F BIOGEN COM Put 325,500 72.95 92,305 56.68 n/a n/a n/a
2016-11-10 2016-09-30 13F BIOGEN COM Put 188,200 11.89 58,912 44.84 n/a n/a n/a
2016-08-12 2016-06-30 13F BIOGEN COM Put 168,200 29.29 40,674 20.10 n/a n/a n/a
2016-05-13 2016-03-31 13F BIOGEN COM Put 130,100 -38.14 33,867 -47.43 n/a n/a n/a
2016-02-12 2015-12-31 13F BIOGEN COM Put 210,300 40.29 64,426 47.28 n/a n/a n/a
2015-11-13 2015-09-30 13F BIOGEN COM Put 149,900 -3.91 43,743 -30.58 n/a n/a n/a
2015-08-13 2015-06-30 13F BIOGEN COM Put 156,000 14.79 63,014 9.81 n/a n/a n/a
2015-05-14 2015-03-31 13F BIOGEN COM Put 135,900 -32.56 57,382 -16.11 n/a n/a n/a
2015-02-17 2014-12-31 13F BIOGEN IDEC COM Put 201,500 -18.26 68,399 -16.12 n/a n/a n/a
2014-11-14 2014-09-30 13F BIOGEN IDEC COM Put 246,500 3.75 81,545 8.85 n/a n/a n/a
2014-08-14 2014-06-30 13F BIOGEN IDEC COM Put 237,600 2.50 74,917 5.67 n/a n/a n/a
2014-05-15 2014-03-31 13F BIOGEN IDEC COM Put 231,800 -6.46 70,900 2.28 n/a n/a n/a
2014-02-14 2013-12-31 13F BIOGEN IDEC COM Put 247,800 -16.11 69,322 -2.53 n/a n/a n/a
2013-11-14 2013-09-30 13F BIOGEN IDEC COM Put 295,400 12.66 71,121 26.05 n/a n/a n/a
2013-08-14 2013-06-30 13F BIOGEN IDEC COM Put 262,200 56,425 n/a n/a n/a
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.