Biogen insiders sold $905K in the past 12 months. How much of their stake is that?

Vested shares across all share classes, held directly and through trusts, LLCs and family members, as reported on SEC Forms 3, 4 and 5. Unvested awards and options are never counted as owned shares.

19 of 21 insiders fully reconciled: starting holdings plus reported transactions match ending holdings (17 exactly, 2 with a minor or footnoted difference). For 2 we show sales but not holdings; the ! icon on their rows explains why. Percentages cover 16 of 21 officers and directors. Left out: Rachid Izzar and Sean Godbout (holdings couldn't be fully reconciled); Priya Singhal (most of their shares vested during the period, so a percentage would mislead); Menelas Pangalos and Michael Parini (held no vested shares at the start). "Still held" compares ending with starting vested shares; a plus sign means the holding grew.

Officer and director open-market sales: $905K across 4,594 shares. Plan status and stated purpose are separate questions, and a sale can have both.

Sales by month

Less than usual: about half of the 5-year average. 2 insiders sold; the average is 2 a year.

Open-market sales (Form 4 code S) by people who were officers or directors, in split-adjusted shares. Earlier years include people who have since left. A sale that an outside holder also reports (a family trust, a fund) is counted with outside holders in every year. Shares, not dollars, are compared, so a change in the stock price doesn't look like a change in selling. Years the filings don't fully cover are shown but left out of the average.

All 1,677 Forms 3, 4 and 5 filed for Biogen (SEC CIK 875045) from Aug 4, 2003 to Oct 5, 2026, retrieved from SEC EDGAR on Oct 9, 2026. Prices are the ones reported in each filing, often weighted averages. 36 filings were left out because Biogen filed them as an owner of another company's stock.

Holdings. Each holding line (a share class plus an owner, such as a trust or LLC) carries its last reported balance forward. Entities first reported during the period start at zero, so transfers between an insider's own trusts don't count as selling. Lines not reported for three years or more are listed separately and left out of totals.

Sales. A sale counts as under a 10b5-1 plan if its footnote cites one or the filing's Rule 10b5-1 box is checked, and as tax-related if its footnote cites tax obligations or sell-to-cover. Shares withheld by the company for taxes are listed separately. Sales with neither attribute are labeled "no plan disclosed".

Full methodology