Marcus Chen
Senior Market Analyst
Senior Market Analyst at 13F Insight. Covers institutional portfolio strategy, 13F filings, and smart money trends.
A note from Marcus
Hi, I'm Marcus. I spent six years on the buy side staring at 13F filings for a hedge fund, and the thing that bothered me most wasn't the work — it was knowing that the average investor never gets to see what I was looking at, even though it's all public.
That's why I'm here. Every research piece you'll see under my name comes from real SEC data, run through real institutional logic, and translated into something you can actually act on. I write long when the data deserves it and short when it doesn't.
If you ever spot a number that looks off, email me. I'd rather be corrected than wrong.
Articles by Marcus Chen (311)
- News
Lilly Endowment Sold $406M in Eli Lilly Stock in Six Weeks — And Still Owns $100B
The Lilly family's philanthropic endowment dumped 376,000 LLY shares worth $406 million between November and December 2025, yet its remaining 92.2 million shares are worth over $100 billion.
- Research
Buffett Dumps 77% of Amazon in His Final Quarter as CEO - Berkshire Hathaway Q4 2025 13F Deep Dive
Berkshire Hathaway's Q4 2025 13F reveals Buffett slashed Amazon by 77%, continued trimming Apple and Bank of America, while adding to Chevron and Chubb — all in his final quarter as CEO.
- Research
Buffett Dumps 77% of Amazon in His Final Quarter as CEO — Berkshire Hathaway Q4 2025 13F Deep Dive
Warren Buffett slashed Amazon by 77% in his final quarter as Berkshire Hathaway CEO, while adding to Chevron, Chubb, and Domino's. Deep dive into the $274.2B Q4 2025 13F filing.
- Research
Soroban Tripled to $14.3B in One Quarter and Built a $2.3B Utility Sleeve Nobody Saw Coming: Inside Mandelblatt's Tech-Utility Barbell
Eric Mandelblatt's Soroban Capital deployed $9.2B in a single quarter — tripling AUM from $5.15B to $14.33B — while building a rare tech-utility barbell with MSFT and AMZN at the top and nine regulated utilities underneath.
- Research
Vanguard's $6.90T Q4 2025 Filing: Mega-Cap Concentration With Broad-Market Breadth
VANGUARD GROUP INC reported $6897.68B in Q4 2025 13F assets with top-10 concentration at 31.23%. We break down what changed and what retail investors can act on.
- Research
Castle Hook Dumped $1.35B in Bitcoin and Built an $8.4B Gold Fortress: Inside the Soros Alumnus's Macro Bet That Doubled Portfolio Size
Josh Donfeld's Castle Hook Partners exited Bitcoin entirely, built a 35% gold allocation, added $8.3B in equity puts, and grew 13F AUM 74% to $24.1B in Q4 2025 — the most dramatic macro pivot of filing season.
- Research
Smead Capital's $4.8B Anti-AI Portfolio: 27.5% Housing, Zero Magnificent Seven, and a 15.5x P/E vs the Market's 27.7x
Smead Capital's Q4 2025 13F reveals a $4.8B portfolio with 27.5% in housing, 20.6% in banks, and just 2.2% in tech. At 15.5x P/E vs the S&P 500's 27.7x, Bill Smead is betting that overlooked value sectors will deliver the same alpha they did after similar discounts in 2015, 2020, and 2022.
- Research
Q4 2025 13F: Bank Exposure Signals Institutions Can't Hide
A non-tech research note on interpreting bank exposure changes in Q4 2025 13F filings: rotation patterns, funding sources, and a checklist to avoid common 13F traps.
- Research
70% of Icahn's $8.45B Sits in Two Energy Companies: Inside the Most Concentrated Non-Tech 13F in Q4 2025
Carl Icahn's Q4 2025 13F reveals extreme energy concentration — IEP and CVR Energy alone account for 70% of his $8.45B portfolio, with zero technology exposure and just 13 holdings.
- Research
Baker Bros Deployed $6.9B Into Pure Biotech in One Quarter: Inside the $17B Healthcare-Only Portfolio That Owns Zero Tech Stocks
Baker Bros Advisors surged 67.8% to $17.08B in Q4 2025 by injecting $6.9B across 19 new biotech positions while maintaining a 100% healthcare portfolio — the largest pure-play biotech fund in 13F filing history.
- Research
Berkshire Hathaway’s Top 10 Holdings in Q4 2025: 88% of $274B in Just Ten Stocks
Berkshire Hathaway’s Q4 2025 13F reveals extreme portfolio concentration — the top 10 holdings account for 88.3% of the $274.2 billion portfolio, with Apple and American Express alone commanding 43%.
- Research
69% in Two Stocks and a $7.4B Buyout Pending: Inside Trian’s Ultra-Concentrated Q4 2025 Activist Portfolio
Nelson Peltz’s Trian Fund holds just 7 stocks worth $3.98B — with 69% concentrated in Janus Henderson and GE Aerospace. The Q4 2025 filing arrives as Peltz takes his #1 holding private for $7.4B while slashing Invesco 80%.
- Research
Hohn Injected $31.9B Into Just 9 Stocks After TCI's Record $18.9B Profit Year: Inside the Most Concentrated $53.6B Portfolio in Hedge Fund History
Chris Hohn's TCI Fund Management more than doubled its US equity portfolio to $53.6B with just 9 holdings in Q4 2025. GE Aerospace alone is a $14.6B bet — the largest new position any hedge fund added last quarter.
- Research
Druckenmiller Dumped META and Bet $247M on Brazil With Leveraged Calls: Inside Duquesne's $4.5B Q4 2025 Macro Rotation
Stanley Druckenmiller exited Meta after one quarter, re-entered Brazil (EWZ) with $247M in shares plus call options, and deployed $914M into new macro ETF positions — financials, equal-weight, and index calls. Duquesne's AUM hit $4.49B with a 43% turnover rate.
- Research
Paulson Deployed $2.7B in One Quarter and Built a $994M Rezdiffra Bet Alongside a $1.3B Gold Mining Empire: Inside the Q4 2025 Comeback
Paulson & Co. surged from $520M and 3 holdings to $3.26B and 9 positions in Q4 2025 — a 527% AUM explosion driven by a near-billion-dollar Madrigal Pharma bet and four gold/antimony miners worth $1.3B.
- Research
Lone Pine Exited META and Deployed $6.4B Across 14 New Stocks: Inside the Tiger Cub's Most Radical Portfolio Reconstruction
Stephen Mandel's Lone Pine Capital dumped its entire $971M Meta Platforms position and opened 14 new positions worth $6.4B in Q4 2025. The portfolio went from 25 to 32 holdings with a strikingly flat concentration — no single stock above 6.82%. A breakdown of the most dramatic single-quarter transformation by any Tiger Cub this filing season.
- Research
Coatue's $15.7B Capital Deployment: Laffont Built a Semiconductor Equipment Empire While Dumping CoreWeave
Philippe Laffont deployed $15.7B across 27 new positions — including a $3.2B semiconductor equipment cluster in LRCX and AMAT — while fully exiting CoreWeave. Coatue's AUM hit an all-time high of $39.96B with top-10 concentration dropping 14.5 points.
- Research
Healthcare Surged 12.7% While Defensives Flatlined: Inside the Q4 2025 Institutional Sector Rotation
The 100 largest institutional investors shifted $49.5 trillion across sectors in Q4 2025. Healthcare was the clear winner at +12.7%, Communication Services gained 8.2%, while Consumer Defensive and Utilities barely moved. Here's the full sector-by-sector breakdown.
- Research
Soros Added 59 Positions and a $415M XOP Bet: Inside the Q4 2025 Breadth Expansion
Soros Fund Management expanded 13F value by 22.93% in Q4 2025, added 59 holdings, and launched a $415M XOP position while keeping Amazon as the top core holding.
- Research
Millennium Rolled $16.6B of QQQ Exposure in One Quarter as Walmart Jumped Into the Top Bucket
Millennium's Q4 2025 13F reveals a $16.6B QQQ sleeve rollover, a $4.23B build in Walmart, and a portfolio that grew to $237.8B while top-10 concentration moved higher.