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45-day lag, survivorship bias, and when copying actually works
Once a quarter, every institutional manager with $100M+ under management has to tell the SEC what they own. Those filings are public. Copying the smartest investors should be easy — except for the lag, the omissions, and the survivorship bias built into who you decide to follow.
A is a quarterly snapshot of an institutional manager's long U.S. equity book. It tells you what they OWNED on the last day of the quarter. It does not tell you when they bought, what they paid, what they short, what they hedge with, or what they sold during the quarter.
Filings are due 45 calendar days after quarter end. By the time you see Berkshire's Q1 holdings, it's mid-May — anywhere from 45 to 135 days after individual trades happened. The most-discussed positions have already moved. The signal is real but stale; treat 13F as a STARTING POINT for research, not as a real-time copy-trade source.
Short positions: invisible (13F is long-only U.S. equities). Cash: not disclosed (you can't see what fraction of the book is in cash, only what's invested). Foreign equities: invisible. Bonds, options without underlying long positions, private positions: invisible. A 'top holding' might be a paired hedge against something else you can't see. The filing is one slice of a portfolio, not the whole portfolio.
The list of 'superinvestors' worth copying is curated AFTER the fact — the failures don't make the list. Long Term Capital Management, Bear Stearns prop, every blown-up hedge fund — none of them appear in the curated lists you see today. So when you read an academic study claiming 'top funds' delivered 4-7% alpha, remember that 'top' was defined retrospectively. The actual ex-ante choice is much harder than it looks ex-post.
Lauren Cohen, Andrea Frazzini, and Christopher Malloy studied whether copying the top holdings of skilled hedge fund managers (after the 45-day filing lag) produced excess returns. They found that portfolios constructed from the top 5 holdings of the most skilled managers — measured by historical risk-adjusted returns — delivered roughly 4-7 percentage points of annualized alpha after the 45-day lag. The paper is the academic basis for the 'follow the smart money' approach, but the authors emphasized two key caveats: (1) the alpha existed only for the highest-conviction top-5 positions, not the full portfolio; (2) identifying the 'most skilled' managers ex-ante was much harder than identifying them ex-post. Source: Cohen, Frazzini & Malloy, 'Hedge Funds and Stock Market Efficiency,' Journal of Political Economy, 2010.
Open the Superinvestors tab. It aggregates the 13F filings of a curated list of well-known long-equity managers. The default view shows: (1) which stocks are held by the most managers (consensus picks), (2) which stocks have the largest aggregate position-size growth quarter-over-quarter (new conviction), and (3) which positions are concentrated as 'top 5' across multiple managers (the highest-signal Cohen/Frazzini/Malloy configuration). Click any name to see their full disclosed long book. Read the consensus column FIRST — multiple skilled managers independently reaching the same conclusion is the academic-literature definition of a smart-money signal.
Buying a stock because Buffett bought it is NOT investing — it's tribal allegiance. You don't see his cost basis, his exit triggers, his portfolio context, or what he hedges with. When the position moves against you, you have no thesis to fall back on, no sell rules of your own, and no understanding of why you're holding. 13F is a SEARCH SHORTCUT — it points you at companies worth investigating yourself. Once you've done the work, you own the position because you understand it, not because someone famous owns it too.
You can be informed by what others are doing — what the smart money is buying — but if you treat their portfolio as your portfolio, you've outsourced your conviction. When the position drops 30%, you have no thesis to fall back on. Use 13F as a starting point for research, not as a substitute for it.
13F filings are quarterly snapshots of institutional long-equity holdings, due 45 days after quarter end. The filing shows what was owned on the last day of the quarter — not when, why, or at what price. 13F doesn't show shorts, cash, foreign equities, bonds, or hedges; you see one slice of the portfolio. Cohen Frazzini Malloy 2010 found roughly 4-7% annualized alpha in the top-5 holdings of the most-skilled managers, after the 45-day lag. Survivorship bias inflates the case: 'top managers' are identified ex-post, after blowups have been removed from the list. Use 13F as a starting point for research; never as a substitute for your own thesis.