BIIB Stock vs the S&P 500: Returns, Risk and Crash History

Named analysts’ rating and price‑target changes on BIIB in the 5 weeks to Oct 12, 2026, shown 30 days after publication (the free analysts’ calls 3 days after). The top‑ranked analysts’ calls are in Exent Gems. See all of the latest analyst upgrades and downgrades.

Of the 1,149 analyst price targets on BIIB set from 2019 until a year ago, 50.9% were reached within 12 months (data to Oct 20, 2026), 17.7 points below the 68.6% hit rate of the median stock in Exent’s study of 794 stocks. Targets that were reached took a median of 63 days. The median target sat 17.3% above the share price on the day it was set.

Where analysts said BIIB would be by now: a year ago, 14 analysts had a price target on BIIB, and the median of their latest targets was $183.50. On Oct 20, 2026 BIIB closed at $243.24, 32.6% above it.

The move on the call runs from the close before the rating change to the close after it; the last column is the stock’s return minus the S&P 500’s over the next three months. Averages of rating changes on BIIB through Sep 15, 2026; analysts are not named here. Do analyst upgrades move stocks?

BIIB beat the consensus earnings‑per‑share estimate in 11 of its last 12 quarterly reports, through the one on Jul 29, 2026, and the revenue estimate in 9 of 12. From the close before each report to the close after it, the stock moved 4.3% on average, up or down, against 6.8% for the average report across the 1,002 US stocks Exent tracks. It rose after 7 of the 12 reports. In 4 of the 11 beats the stock still fell.

Reported earnings per share against the consensus estimate, revenue surprise in percent, and the stock’s price change over the two sessions around the report. How stocks move after earnings

In fiscal 2025 (the year to Dec 31, 2025), BIIB’s largest reported region was Non-US, with 60.1% of its $5.9 billion revenue. By region: Non-US 60.1%; United States 39.9%.

By business, the largest segment was MS Product Revenues, with 42.0% of $9.6 billion revenue (−7.1% on the year before).

From BIIB’s annual filings; segment growth compares fiscal 2025 with the year before. Regions are as each company reports them, so one company’s “Asia Pacific” is not another’s. China counts the regions a company reports as China, Greater China or Hong Kong; a separately reported Taiwan is not counted. Which S&P 500 companies depend most on China?

As of Oct 20, 2026, 19 members of Congress had disclosed 88 trades in BIIB (47 buys and 41 sales) in STOCK Act disclosures filed with the House and Senate. The latest public trade is dated Aug 18, 2026.

Amounts are the ranges members report, not exact values. The STOCK Act gives members up to 45 days to disclose a trade, so trades appear weeks after they are made. See every member’s disclosed trades

3 trades in BIIB disclosed in the last 30 days are in Exent Radar.

In the 12 months to Oct 20, 2026, BIIB insiders made 1 open‑market purchase worth $585 by 1 insider and 4 sales worth $905,414, according to SEC Form 4 filings.

After the 21 insider purchases of $10,000 or more since 2012, BIIB lagged the S&P 500 by an average of 9.7 percentage points over the next 12 months; 24% of them were followed by a beat. Across all 17,865 insider purchases in Exent’s study, the average was +17.2% and the median +1.0% against the index.

The table lists the latest open‑market purchases on record, leaving out the last 30 days. The chart counts Form 4 purchases and sales by calendar quarter. Purchases are open‑market buys; sales include planned sales under 10b5‑1 trading plans. Do insider buys beat the market?

As of the Sep 30, 2026 settlement date, 4.07% of BIIB’s float was sold short: 6.0 million shares, or 4.9 days of average trading volume to cover. A year earlier (Oct 15, 2025) it was 3.54%. The median across the 997 US stocks Exent tracks was 4.77%, so BIIB is less heavily shorted than most.

From FINRA short‑interest reports, filed twice a month; the bars show the short share of the float at each month‑end. Days to cover divides the shares short by the average daily volume. The most shorted stocks

At the end of Q2 2026 (Jun 30, 2026), 1,103 institutions reported holding BIIB in 13F filings, up 40 from the quarter before and up from 919 a year earlier. Their reported holdings add up to 97.2% of BIIB’s shares. In the quarter 552 institutions added to their positions and 305 cut them.

Investment managers with over $100 million in US equities file 13F reports within 45 days of each quarter end, so this is the latest complete quarter. Holdings can add up to more than 100% when shares are lent and counted twice. Which stocks institutions are buying and selling

BIIB’s diluted share count fell 9.1% over the five fiscal years to fiscal 2025 and rose 0.5% in fiscal 2025 alone. Each share now owns a larger slice of the company. The median change across the 1,005 US stocks Exent tracks was −0.1%.

Stock‑based compensation was $290.8 million in fiscal 2025, 3.0% of revenue. BIIB did not buy back shares in fiscal 2025.

Weighted‑average diluted shares from BIIB’s annual income statements; stock‑based compensation and buybacks from its cash‑flow statement. Stock dilution and stock‑based compensation, explained

In Exent’s Oct 20, 2026 snapshot, BIIB’s Altman Z‑score was 3.10, in the safe zone (where 465 of the 794 non‑financial US stocks Exent tracks sit). Its Piotroski F‑score was 4 out of 9; 88% of scored stocks reach 4 or more.

The Altman Z‑score combines five balance‑sheet and earnings ratios into one bankruptcy‑risk score: below 1.81 is the distress zone, 1.81–2.99 grey, above 2.99 safe. It is not meaningful for banks, insurers and REITs. The Piotroski F‑score counts nine yes/no tests of profitability, leverage and efficiency; 8–9 is strong, 0–2 weak. Both come from the latest annual statements. Which stocks have the highest bankruptcy risk?

On its latest earnings call (Jul 29, 2026), BIIB’s executives and analysts did not mention AI, against 0 on the call before (Apr 29, 2026); the average across 455 S&P 500 calls that quarter was 12.9. After AI, the most mentioned topic was china (2). Tariffs and recession did not come up.

Word counts in the full transcript of each call, prepared remarks and Q&A, newest first. “AI” also counts generative AI and large language models; “AI agents” counts agentic AI. Which companies talk most about AI?

As of Oct 20, 2026, 56 of the 304 ETFs Exent tracks held BIIB. Its largest weight is in FTXH (First Trust Nasdaq Pharmaceuticals ETF), at 3.84% of the fund.

Owning several of these funds stacks the same position. How much do VOO, QQQ and VTI overlap?

Christopher A. Viehbacher, BIIB’s President and Chief Executive Officer, received total pay of $23.6 million for fiscal 2025, down 2.2% from $24.2 million for fiscal 2024, according to the company’s proxy statement filed with the SEC on Apr 28, 2026. 78% of it came as stock and option awards, valued when they were granted rather than when they pay out. The median CEO pay across the 378 S&P 500 companies Exent tracks was $17.2 million.

Figures from the summary compensation table of the proxy statement; awards count at their grant‑date value, so one large multi‑year grant can make a single year stand out. CEO pay across the S&P 500