Sarah Mitchell
Education Editor
Investment Education Editor at 13F Insight. Breaks down complex institutional data into actionable insights for individual investors.
A note from Sarah
Hi, I'm Sarah. I spent four years at Vanguard's Investor Education team, where my whole job was making 401(k) statements feel less like tax forms and more like something a person could actually understand.
I'm here at 13F Insight to do the same thing for institutional data. If you've ever read a headline like "Berkshire Bought Apple" and thought "okay but what does that actually mean for me," that's the gap I want to close.
I'll never assume you know what a CUSIP is. I'll always tell you why a number matters before I give you the number. And if a guide of mine ever leaves you more confused than you started, that's on me — let me know and I'll rewrite it.
Articles by Sarah Mitchell (818)
- Learn
13F Filing Season Playbook: What Matters on Each Deadline
Filing season is only useful if you know which deadlines matter and which position changes deserve your attention first.
- Learn
What Top-Ten Overlap Between Passive Giants Really Tells You
When passive giants share most of their top ten, the overlap is not a boring coincidence. It is a market-structure signal that helps define the baseline every active portfolio should be judged against.
- Learn
How to Compare Vanguard, BlackRock, and State Street 13Fs Without Getting Fooled
Comparing passive giants by raw dollar positions will usually tell you what is biggest in the market, not who is making the most differentiated decision. The right comparison starts elsewhere.
- Learn
Why a New Position in a Mega-Fund 13F May Not Be a New Bet
A new holding in a trillion-dollar 13F can look like a stock-picking signal. In practice, it often reflects benchmark changes, wrapper shifts, or position-size thresholds rather than a fresh thesis.
- Learn
How to Read Index-Manager 13Fs Without Mistaking Scale for Skill
Big 13F filings from index managers can look like genius stock-picking. Most of the time, they are a map of benchmark exposure, cash flows, and rebalancing pressure instead.
- Learn
Insider Trading and Form 4: What It Tells You About a Company
Form 4 filings track insider buys, sells, and exercises at public companies. Learn how to interpret insider transactions and what they signal about company outlook.
- Learn
Understanding Portfolio Concentration: When Fewer Holdings Signal Stronger Conviction
Some of the best-performing institutional investors hold concentrated portfolios. Learn what portfolio concentration reveals and when it matters most.
- Learn
What Is a 13F Filing? A Beginner's Guide to Tracking Institutional Holdings
13F filings reveal what the world's largest institutional investors own. Learn how to read them, when they're filed, and how to use them for smarter investing.
- Research
Wellington Management's $571B Portfolio: The Most Balanced Mega-Fund You've Never Analyzed
Wellington Management closed Q4 2025 with $570.66B across 7,580 positions. Unlike peers chasing NVIDIA, Wellington's top holding is just 4.9% of portfolio — true diversification at scale.
- Learn
How to Compare Two 13F Filings Side by Side: A Practical Guide
Learn how to systematically compare quarterly 13F filings to spot portfolio changes, new positions, exits, and sector shifts that signal institutional investor strategy.
- Learn
How to Read a Filer's Quarterly AUM History on 13F Insight
Learn how to interpret AUM history charts on filer detail pages, spot growth trends, and understand what drives institutional portfolio changes.
- News
Lilly Endowment Has Sold $111.8B in LLY Stock — But It's Not a Bearish Signal
The Lilly Endowment, one of America's largest charitable foundations, has systematically sold over $111 billion in Eli Lilly shares since 2003. This is not insider pessimism—it's foundation law in action.
- Learn
How to Spot Insider Buying Signals: A Beginner's Guide to Form 4 Data
Learn how to interpret insider buying transactions on Form 4 filings. Discover what makes a buy meaningful, how to filter noise, and how to use insider trading data to inform your investment decisions.
- Learn
Understanding Portfolio Concentration: When Fewer Holdings Mean More
Learn how institutional investors use portfolio concentration as a strategy, and how to spot concentrated vs. diversified portfolios on 13F Insight.
- Learn
13F Filing Deadlines: When Institutional Holdings Data Is Released
A calendar guide to 13F filing deadlines, amendment windows, and how to plan your institutional holdings research around quarterly filing season for maximum efficiency.
- Learn
How to Use Watchlists to Monitor Smart Money Moves
A step-by-step guide to setting up and using 13F Insight watchlists to track institutional filers and stocks. Learn what to add, how to time your research around filing season, and how to interpret watchlist activity.
- Learn
What Is a Whale Score and How to Use It
A practical guide to using whale scores for screening, comparing, and evaluating institutional 13F filers. Learn when high scores are misleading and how to combine scores with other data for smarter research.
- Learn
How to Track Institutional Buying and Selling With 13F Data
Learn how to use quarter-over-quarter changes in 13F filings to identify when institutional investors are accumulating or distributing positions, and why share count changes matter more than value changes.
- Learn
How to Track Hedge Fund Portfolios Using 13F Data: A Step-by-Step Guide
Want to see what Berkshire Hathaway, Citadel, or Bridgewater is buying? 13F filings let you peek inside hedge fund portfolios every quarter. Here's how to find, read, and interpret the data.