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 (542)
- 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.
- Research
Citadel's $666B Q4 2025 Rebalance: Cutting Index Hedges, Adding Alphabet and Semis
Citadel Advisors ended Q4 2025 with a $665.9B 13F portfolio, up 1.33% QoQ, while reducing top-position concentration. The filing shows a clear rebalance: heavier Alphabet and semiconductor exposure, paired with lower SPY/QQQ index hedge weight.
- Research
Thoma Bravo Put 95.4% Into One Stock: Inside the $9.7B SailPoint Concentration in Q4 2025
THOMA BRAVO, L.P. filed a highly concentrated Q4 2025 13F: 95.4% in SailPoint, 99.1% in top two names, and only three reported holdings. We break down what changed from Q3, why MeridianLink disappeared, and how to read sponsor-style filings versus hedge-fund-style filings.
- Research
No Q4 Filing: Burry Ended Scion After Concentrating 96.7% Into PLTR+NVDA Puts
Scion filed no Q4 2025 13F by Feb 19, 2026. Burry's final filing concentrated 96.7% into PLTR/NVDA put exposure, then the fund deregistered seven days later—an extreme final act with unusual conviction and timing.
- Research
Viking Global's Amazon Boomerang: Halvorsen Sold 3.9M Shares in Q3, Bought Them Back in Q4
Viking Global's Q4 2025 13F reveals a portfolio in violent transition: Amazon re-entered after Q3 exit, Meta dumped for Alphabet, banks slashed 60%, and 21 new positions opened. Inside the $37.7B fund's 56% turnover rate.
- Research
Ackman's $1.76B Meta Gambit: Inside Pershing Square's Q4 2025 All-In AI Pivot
Bill Ackman's Pershing Square filed its Q4 2025 13F revealing a brand-new $1.76 billion Meta Platforms position, a 65% Amazon increase, 50% Brookfield accumulation, and a full Chipotle exit — pushing tech exposure to 55% of the $15.5B portfolio.
- Research
Renaissance Slashes NVIDIA 85%, Exits Meta Entirely: Inside the Quant Giant's Most Radical Portfolio Overhaul Since the Quant Quake
Renaissance Technologies' Q4 2025 13F filing reveals the most radical portfolio overhaul in years: an 85% NVIDIA slash, complete Meta exit, 749 positions liquidated, and massive defensive pivots to Costco (+5,221%) and Netflix (+2,545%) — all in the aftermath of October's devastating Quant Quake.
- Research
Bridgewater Associates Q4 2025 13F Deep Dive: The $4.8 Billion SPY Bet and Dalio's Portfolio Transformation
Bridgewater Associates 10x'd their S&P 500 ETF position to $4.8 billion — making SPY 22% of the entire portfolio. Inside the Q4 2024 13F: massive sector rotation, 168 position exits, new Tesla and Robinhood bets, and a consumer defensive retreat that reshaped a $21.8 billion fund.
- Research
Berkshire Hathaway Q4 2025 13F Deep Dive: Inside Buffett's $267 Billion Portfolio
A position-by-position analysis of Berkshire Hathaway's Q4 2024 13F filing. Apple selling stops at 300M shares, BAC reduction continues at -14.7%, Constellation Brands enters as the only new buy, and the top 5 holdings dominate at 72% of the $267B portfolio.
- Research
Whale Fund Filings Decoded: What Buffett, Dalio, Griffin, and Simons Revealed in Q4 2025
The February 14 deadline has passed and every major whale fund has filed. Berkshire stopped selling Apple at 300M shares, Bridgewater made a 10x SPY bet, Renaissance doubled down on Robinhood and Spotify, Ackman added Nike, Viking rotated massively into financials, and Burry went all-in on China. Here is what the data reveals.